<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux-toradex.git/include/uapi/sound, branch v4.15-rc6</title>
<subtitle>Linux kernel for Apalis and Colibri modules</subtitle>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/'/>
<entry>
<title>tools/headers: Synchronize kernel ABI headers</title>
<updated>2017-11-04T08:27:46+00:00</updated>
<author>
<name>Ingo Molnar</name>
<email>mingo@kernel.org</email>
</author>
<published>2017-11-03T11:18:37+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=fb7df12d645cfba6a76a45fdcc7e3f7fbbcda661'/>
<id>fb7df12d645cfba6a76a45fdcc7e3f7fbbcda661</id>
<content type='text'>
After the SPDX license tags were added a number of tooling headers got out of
sync with their kernel variants, generating lots of build warnings.

Sync them:

 - tools/arch/x86/include/asm/disabled-features.h,
   tools/arch/x86/include/asm/required-features.h,
   tools/include/linux/hash.h:

     Remove the SPDX tag where the kernel version does not have it.

 - tools/include/asm-generic/bitops/__fls.h,
   tools/include/asm-generic/bitops/arch_hweight.h,
   tools/include/asm-generic/bitops/const_hweight.h,
   tools/include/asm-generic/bitops/fls.h,
   tools/include/asm-generic/bitops/fls64.h,
   tools/include/uapi/asm-generic/ioctls.h,
   tools/include/uapi/asm-generic/mman-common.h,
   tools/include/uapi/sound/asound.h,
   tools/include/uapi/linux/kvm.h,
   tools/include/uapi/linux/perf_event.h,
   tools/include/uapi/linux/sched.h,
   tools/include/uapi/linux/vhost.h,
   tools/include/uapi/sound/asound.h:

     Add the SPDX tag of the respective kernel header.

 - tools/include/uapi/linux/bpf_common.h,
   tools/include/uapi/linux/fcntl.h,
   tools/include/uapi/linux/hw_breakpoint.h,
   tools/include/uapi/linux/mman.h,
   tools/include/uapi/linux/stat.h,

     Change the tag to the kernel header version:

       -/* SPDX-License-Identifier: GPL-2.0 */
       +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */

Also sync other header details:

 - include/uapi/sound/asound.h:

     Fix pointless end of line whitespace noise the header grew in this cycle.

 - tools/arch/x86/lib/memcpy_64.S:

     Sync the code and add tools/include/asm/export.h with dummy wrappers
     to support building the kernel side code in a tooling header environment.

 - tools/include/uapi/asm-generic/mman.h,
   tools/include/uapi/linux/bpf.h:

     Sync other details that don't impact tooling's use of the ABIs.

Acked-by: Arnaldo Carvalho de Melo &lt;acme@redhat.com&gt;
Cc: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
Cc: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Cc: Peter Zijlstra &lt;peterz@infradead.org&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: Peter Zijlstra &lt;peterz@infradead.org&gt;
Cc: Namhyung Kim &lt;namhyung@kernel.org&gt;
Cc: Jiri Olsa &lt;jolsa@redhat.com&gt;
Cc: Stephen Rothwell &lt;sfr@canb.auug.org.au&gt;
Signed-off-by: Ingo Molnar &lt;mingo@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
After the SPDX license tags were added a number of tooling headers got out of
sync with their kernel variants, generating lots of build warnings.

Sync them:

 - tools/arch/x86/include/asm/disabled-features.h,
   tools/arch/x86/include/asm/required-features.h,
   tools/include/linux/hash.h:

     Remove the SPDX tag where the kernel version does not have it.

 - tools/include/asm-generic/bitops/__fls.h,
   tools/include/asm-generic/bitops/arch_hweight.h,
   tools/include/asm-generic/bitops/const_hweight.h,
   tools/include/asm-generic/bitops/fls.h,
   tools/include/asm-generic/bitops/fls64.h,
   tools/include/uapi/asm-generic/ioctls.h,
   tools/include/uapi/asm-generic/mman-common.h,
   tools/include/uapi/sound/asound.h,
   tools/include/uapi/linux/kvm.h,
   tools/include/uapi/linux/perf_event.h,
   tools/include/uapi/linux/sched.h,
   tools/include/uapi/linux/vhost.h,
   tools/include/uapi/sound/asound.h:

     Add the SPDX tag of the respective kernel header.

 - tools/include/uapi/linux/bpf_common.h,
   tools/include/uapi/linux/fcntl.h,
   tools/include/uapi/linux/hw_breakpoint.h,
   tools/include/uapi/linux/mman.h,
   tools/include/uapi/linux/stat.h,

     Change the tag to the kernel header version:

       -/* SPDX-License-Identifier: GPL-2.0 */
       +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */

Also sync other header details:

 - include/uapi/sound/asound.h:

     Fix pointless end of line whitespace noise the header grew in this cycle.

 - tools/arch/x86/lib/memcpy_64.S:

     Sync the code and add tools/include/asm/export.h with dummy wrappers
     to support building the kernel side code in a tooling header environment.

 - tools/include/uapi/asm-generic/mman.h,
   tools/include/uapi/linux/bpf.h:

     Sync other details that don't impact tooling's use of the ABIs.

Acked-by: Arnaldo Carvalho de Melo &lt;acme@redhat.com&gt;
Cc: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
Cc: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
Cc: Peter Zijlstra &lt;peterz@infradead.org&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: Peter Zijlstra &lt;peterz@infradead.org&gt;
Cc: Namhyung Kim &lt;namhyung@kernel.org&gt;
Cc: Jiri Olsa &lt;jolsa@redhat.com&gt;
Cc: Stephen Rothwell &lt;sfr@canb.auug.org.au&gt;
Signed-off-by: Ingo Molnar &lt;mingo@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>License cleanup: add SPDX license identifier to uapi header files with a license</title>
<updated>2017-11-02T10:20:11+00:00</updated>
<author>
<name>Greg Kroah-Hartman</name>
<email>gregkh@linuxfoundation.org</email>
</author>
<published>2017-11-01T14:09:13+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=e2be04c7f9958dde770eeb8b30e829ca969b37bb'/>
<id>e2be04c7f9958dde770eeb8b30e829ca969b37bb</id>
<content type='text'>
Many user space API headers have licensing information, which is either
incomplete, badly formatted or just a shorthand for referring to the
license under which the file is supposed to be.  This makes it hard for
compliance tools to determine the correct license.

Update these files with an SPDX license identifier.  The identifier was
chosen based on the license information in the file.

GPL/LGPL licensed headers get the matching GPL/LGPL SPDX license
identifier with the added 'WITH Linux-syscall-note' exception, which is
the officially assigned exception identifier for the kernel syscall
exception:

   NOTE! This copyright does *not* cover user programs that use kernel
   services by normal system calls - this is merely considered normal use
   of the kernel, and does *not* fall under the heading of "derived work".

This exception makes it possible to include GPL headers into non GPL
code, without confusing license compliance tools.

Headers which have either explicit dual licensing or are just licensed
under a non GPL license are updated with the corresponding SPDX
identifier and the GPLv2 with syscall exception identifier.  The format
is:
        ((GPL-2.0 WITH Linux-syscall-note) OR SPDX-ID-OF-OTHER-LICENSE)

SPDX license identifiers are a legally binding shorthand, which can be
used instead of the full boiler plate text.  The update does not remove
existing license information as this has to be done on a case by case
basis and the copyright holders might have to be consulted. This will
happen in a separate step.

This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.  See the previous patch in this series for the
methodology of how this patch was researched.

Reviewed-by: Kate Stewart &lt;kstewart@linuxfoundation.org&gt;
Reviewed-by: Philippe Ombredanne &lt;pombredanne@nexb.com&gt;
Reviewed-by: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Many user space API headers have licensing information, which is either
incomplete, badly formatted or just a shorthand for referring to the
license under which the file is supposed to be.  This makes it hard for
compliance tools to determine the correct license.

Update these files with an SPDX license identifier.  The identifier was
chosen based on the license information in the file.

GPL/LGPL licensed headers get the matching GPL/LGPL SPDX license
identifier with the added 'WITH Linux-syscall-note' exception, which is
the officially assigned exception identifier for the kernel syscall
exception:

   NOTE! This copyright does *not* cover user programs that use kernel
   services by normal system calls - this is merely considered normal use
   of the kernel, and does *not* fall under the heading of "derived work".

This exception makes it possible to include GPL headers into non GPL
code, without confusing license compliance tools.

Headers which have either explicit dual licensing or are just licensed
under a non GPL license are updated with the corresponding SPDX
identifier and the GPLv2 with syscall exception identifier.  The format
is:
        ((GPL-2.0 WITH Linux-syscall-note) OR SPDX-ID-OF-OTHER-LICENSE)

SPDX license identifiers are a legally binding shorthand, which can be
used instead of the full boiler plate text.  The update does not remove
existing license information as this has to be done on a case by case
basis and the copyright holders might have to be consulted. This will
happen in a separate step.

This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.  See the previous patch in this series for the
methodology of how this patch was researched.

Reviewed-by: Kate Stewart &lt;kstewart@linuxfoundation.org&gt;
Reviewed-by: Philippe Ombredanne &lt;pombredanne@nexb.com&gt;
Reviewed-by: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>License cleanup: add SPDX license identifier to uapi header files with no license</title>
<updated>2017-11-02T10:19:54+00:00</updated>
<author>
<name>Greg Kroah-Hartman</name>
<email>gregkh@linuxfoundation.org</email>
</author>
<published>2017-11-01T14:08:43+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=6f52b16c5b29b89d92c0e7236f4655dc8491ad70'/>
<id>6f52b16c5b29b89d92c0e7236f4655dc8491ad70</id>
<content type='text'>
Many user space API headers are missing licensing information, which
makes it hard for compliance tools to determine the correct license.

By default are files without license information under the default
license of the kernel, which is GPLV2.  Marking them GPLV2 would exclude
them from being included in non GPLV2 code, which is obviously not
intended. The user space API headers fall under the syscall exception
which is in the kernels COPYING file:

   NOTE! This copyright does *not* cover user programs that use kernel
   services by normal system calls - this is merely considered normal use
   of the kernel, and does *not* fall under the heading of "derived work".

otherwise syscall usage would not be possible.

Update the files which contain no license information with an SPDX
license identifier.  The chosen identifier is 'GPL-2.0 WITH
Linux-syscall-note' which is the officially assigned identifier for the
Linux syscall exception.  SPDX license identifiers are a legally binding
shorthand, which can be used instead of the full boiler plate text.

This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.  See the previous patch in this series for the
methodology of how this patch was researched.

Reviewed-by: Kate Stewart &lt;kstewart@linuxfoundation.org&gt;
Reviewed-by: Philippe Ombredanne &lt;pombredanne@nexb.com&gt;
Reviewed-by: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Many user space API headers are missing licensing information, which
makes it hard for compliance tools to determine the correct license.

By default are files without license information under the default
license of the kernel, which is GPLV2.  Marking them GPLV2 would exclude
them from being included in non GPLV2 code, which is obviously not
intended. The user space API headers fall under the syscall exception
which is in the kernels COPYING file:

   NOTE! This copyright does *not* cover user programs that use kernel
   services by normal system calls - this is merely considered normal use
   of the kernel, and does *not* fall under the heading of "derived work".

otherwise syscall usage would not be possible.

Update the files which contain no license information with an SPDX
license identifier.  The chosen identifier is 'GPL-2.0 WITH
Linux-syscall-note' which is the officially assigned identifier for the
Linux syscall exception.  SPDX license identifiers are a legally binding
shorthand, which can be used instead of the full boiler plate text.

This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.  See the previous patch in this series for the
methodology of how this patch was researched.

Reviewed-by: Kate Stewart &lt;kstewart@linuxfoundation.org&gt;
Reviewed-by: Philippe Ombredanne &lt;pombredanne@nexb.com&gt;
Reviewed-by: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Signed-off-by: Greg Kroah-Hartman &lt;gregkh@linuxfoundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge remote-tracking branch 'asoc/topic/intel' into asoc-next</title>
<updated>2017-09-01T11:12:19+00:00</updated>
<author>
<name>Mark Brown</name>
<email>broonie@kernel.org</email>
</author>
<published>2017-09-01T11:12:19+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=460f623a6e3cab02c3cda52cf64094a96afece4e'/>
<id>460f623a6e3cab02c3cda52cf64094a96afece4e</id>
<content type='text'>
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
</pre>
</div>
</content>
</entry>
<entry>
<title>ASoC: Intel: uapi: Add new tokens for module common data</title>
<updated>2017-08-25T13:53:51+00:00</updated>
<author>
<name>Shreyas NC</name>
<email>shreyas.nc@intel.com</email>
</author>
<published>2017-08-23T14:03:49+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=3d52a7924172adf651eda8f1c95ff38146059307'/>
<id>3d52a7924172adf651eda8f1c95ff38146059307</id>
<content type='text'>
The module private data can be modelled independent of its instances so
that it can be reused by the module instances. So move module data to
common manifest which can be referenced by the module instances.

This requires new tokens to be defined to accommodate these changes. The
new tokens will specify buffer sizes, DSP cycles and respective indexes
corresponding to the pcm params in the topology manifest so that driver
need not compute them.

Signed-off-by: Shreyas NC &lt;shreyas.nc@intel.com&gt;
Signed-off-by: Guneshwor Singh &lt;guneshwor.o.singh@intel.com&gt;
Acked-By: Vinod Koul &lt;vinod.koul@intel.com&gt;
Signed-off-by: Mark Brown &lt;broonie@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The module private data can be modelled independent of its instances so
that it can be reused by the module instances. So move module data to
common manifest which can be referenced by the module instances.

This requires new tokens to be defined to accommodate these changes. The
new tokens will specify buffer sizes, DSP cycles and respective indexes
corresponding to the pcm params in the topology manifest so that driver
need not compute them.

Signed-off-by: Shreyas NC &lt;shreyas.nc@intel.com&gt;
Signed-off-by: Guneshwor Singh &lt;guneshwor.o.singh@intel.com&gt;
Acked-By: Vinod Koul &lt;vinod.koul@intel.com&gt;
Signed-off-by: Mark Brown &lt;broonie@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge tag 'asoc-v4.13' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound into for-linus</title>
<updated>2017-07-03T17:51:42+00:00</updated>
<author>
<name>Takashi Iwai</name>
<email>tiwai@suse.de</email>
</author>
<published>2017-07-03T17:51:42+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=818a23e3882b1bf65d1719e407be04716e69a4d5'/>
<id>818a23e3882b1bf65d1719e407be04716e69a4d5</id>
<content type='text'>
ASoC: Updates for v4.13

The big news with this release is the of-graph card, this provides a
replacement for simple-card that is much more flexibile and scalable,
allowing many more systems to use a generic sound card than was possible
before:

 - The of-graph card, finally merged after a long and dedicated effort
   by Morimoto-san.
 - New widget types intended mainly for use with DSPs.
 - New drivers for Allwinner V3s SoCs, Ensonic ES8316, several classes
   of x86 machine, Rockchip PDM controllers, STM32 I2S and S/PDIF
   controllers and ZTE AUD96P22 CODECs.
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
ASoC: Updates for v4.13

The big news with this release is the of-graph card, this provides a
replacement for simple-card that is much more flexibile and scalable,
allowing many more systems to use a generic sound card than was possible
before:

 - The of-graph card, finally merged after a long and dedicated effort
   by Morimoto-san.
 - New widget types intended mainly for use with DSPs.
 - New drivers for Allwinner V3s SoCs, Ensonic ES8316, several classes
   of x86 machine, Rockchip PDM controllers, STM32 I2S and S/PDIF
   controllers and ZTE AUD96P22 CODECs.
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge remote-tracking branch 'asoc/topic/intel' into asoc-next</title>
<updated>2017-07-03T15:51:30+00:00</updated>
<author>
<name>Mark Brown</name>
<email>broonie@kernel.org</email>
</author>
<published>2017-07-03T15:51:30+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=2016d5ed401133539779d8a070abbe42fe9cb3da'/>
<id>2016d5ed401133539779d8a070abbe42fe9cb3da</id>
<content type='text'>
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
</pre>
</div>
</content>
</entry>
<entry>
<title>ASoC: dapm: Add new widget type for constructing DAPM graphs on DSPs.</title>
<updated>2017-06-30T10:55:20+00:00</updated>
<author>
<name>Liam Girdwood</name>
<email>liam.r.girdwood@linux.intel.com</email>
</author>
<published>2017-06-29T13:22:24+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=8a70b4544ef4f094cc2c52734e097cc358f56603'/>
<id>8a70b4544ef4f094cc2c52734e097cc358f56603</id>
<content type='text'>
Add some DAPM widget types to better support the construction of DAPM
graphs within DSPs.

Signed-off-by: Liam Girdwood &lt;liam.r.girdwood@linux.intel.com&gt;
Signed-off-by: Mark Brown &lt;broonie@kernel.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Add some DAPM widget types to better support the construction of DAPM
graphs within DSPs.

Signed-off-by: Liam Girdwood &lt;liam.r.girdwood@linux.intel.com&gt;
Signed-off-by: Mark Brown &lt;broonie@kernel.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ALSA: pcm: Add an ioctl to specify the supported protocol version</title>
<updated>2017-06-27T11:55:46+00:00</updated>
<author>
<name>Takashi Iwai</name>
<email>tiwai@suse.de</email>
</author>
<published>2017-06-19T21:11:54+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=4b671f57747468d7c810caaf955f79ff1aece4d4'/>
<id>4b671f57747468d7c810caaf955f79ff1aece4d4</id>
<content type='text'>
We have an ioctl to inform the PCM protocol version the running kernel
supports, but there is no way to know which protocol version the
user-space can understand.  This lack of information caused headaches
in the past when we tried to extend the ABI.  For example, because we
couldn't guarantee the validity of the reserved bytes, we had to
introduce a new ioctl SNDRV_PCM_IOCTL_STATUS_EXT for assigning a few
new fields in the formerly reserved bits.  If we could know that it's
a new alsa-lib, we could assume the availability of the new fields,
thus we could have reused the existing SNDRV_PCM_IOCTL_STATUS.

In order to improve the ABI extensibility, this patch adds a new ioctl
for user-space to inform its supporting protocol version to the
kernel.  By reporting the supported protocol from user-space, the
kernel can judge which feature should be provided and which not.

With the addition of the new ioctl, the PCM protocol version is bumped
to 2.0.14, too.  User-space checks the kernel protocol version via
SNDRV_PCM_INFO_PVERSION, then it sets the supported version back via
SNDRV_PCM_INFO_USER_PVERSION.

Reviewed-by: Takashi Sakamoto &lt;o-takashi@sakamocchi.jp&gt;
Signed-off-by: Takashi Iwai &lt;tiwai@suse.de&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
We have an ioctl to inform the PCM protocol version the running kernel
supports, but there is no way to know which protocol version the
user-space can understand.  This lack of information caused headaches
in the past when we tried to extend the ABI.  For example, because we
couldn't guarantee the validity of the reserved bytes, we had to
introduce a new ioctl SNDRV_PCM_IOCTL_STATUS_EXT for assigning a few
new fields in the formerly reserved bits.  If we could know that it's
a new alsa-lib, we could assume the availability of the new fields,
thus we could have reused the existing SNDRV_PCM_IOCTL_STATUS.

In order to improve the ABI extensibility, this patch adds a new ioctl
for user-space to inform its supporting protocol version to the
kernel.  By reporting the supported protocol from user-space, the
kernel can judge which feature should be provided and which not.

With the addition of the new ioctl, the PCM protocol version is bumped
to 2.0.14, too.  User-space checks the kernel protocol version via
SNDRV_PCM_INFO_PVERSION, then it sets the supported version back via
SNDRV_PCM_INFO_USER_PVERSION.

Reviewed-by: Takashi Sakamoto &lt;o-takashi@sakamocchi.jp&gt;
Signed-off-by: Takashi Iwai &lt;tiwai@suse.de&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ALSA: pcm: Add the explicit appl_ptr sync support</title>
<updated>2017-06-23T13:39:47+00:00</updated>
<author>
<name>Takashi Iwai</name>
<email>tiwai@suse.de</email>
</author>
<published>2017-06-19T20:39:18+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=42f945970af9df6216e3d771b4df371d02d8742c'/>
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Currently x86 platforms use the PCM status/control mmaps for
transferring the PCM status and appl_ptr between kernel and
user-spaces.  The mmap is a most efficient way of communication, but
it has a drawback per its nature, namely, it can't notify the change
explicitly to kernel.

The lack of appl_ptr update notification is a problem on a few
existing drivers, but it's mostly a small issue and negligible.
However, a new type of driver that uses DSP for a deep buffer
management requires the exact position of appl_ptr for calculating the
buffer prefetch size, and the asynchronous appl_ptr update between
kernel and user-spaces becomes a significant problem for it.

How can we enforce user-space to report the appl_ptr update?  The way
is relatively simple.  Just by disabling the PCM control mmap, the
user-space is supposed to fall back to the mode using SYNC_PTR ioctl,
and the kernel gets control over that.  This fallback mode is used in
all non-x86 platforms as default, and also in the 32bit compatible
model on all platforms including x86.  It's been implemented already
over a decade, so we can say it's fairly safe and stably working.

With the help of the knowledge above, this patch introduces a new PCM
info flag SNDRV_PCM_INFO_SYNC_APPLPTR for achieving the appl_ptr sync
from user-space.  When a driver sets this flag at open, the PCM status
/ control mmap is disabled, which effectively switches to SYNC_PTR
mode in user-space side.

In this version, both PCM status and control mmaps are disabled
although only the latter, control mmap, is the target.  It's because
the current alsa-lib implementation supposes that both status and
control mmaps are always coupled, thus it handles a fatal error when
only one of them fails.

Of course, the disablement of the status/control mmaps may bring a
slight performance overhead.  Thus, as of now, this should be used
only for the dedicated devices that deserves.

Note that the disablement of mmap is a sort of workaround.  In the
later patch, we'll introduce the way to identify the protocol version
alsa-lib supports, and keep mmap working while the sync_ptr is
performed together.

Reviewed-by: Takashi Sakamoto &lt;o-takashi@sakamocchi.jp&gt;
Signed-off-by: Takashi Iwai &lt;tiwai@suse.de&gt;
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Currently x86 platforms use the PCM status/control mmaps for
transferring the PCM status and appl_ptr between kernel and
user-spaces.  The mmap is a most efficient way of communication, but
it has a drawback per its nature, namely, it can't notify the change
explicitly to kernel.

The lack of appl_ptr update notification is a problem on a few
existing drivers, but it's mostly a small issue and negligible.
However, a new type of driver that uses DSP for a deep buffer
management requires the exact position of appl_ptr for calculating the
buffer prefetch size, and the asynchronous appl_ptr update between
kernel and user-spaces becomes a significant problem for it.

How can we enforce user-space to report the appl_ptr update?  The way
is relatively simple.  Just by disabling the PCM control mmap, the
user-space is supposed to fall back to the mode using SYNC_PTR ioctl,
and the kernel gets control over that.  This fallback mode is used in
all non-x86 platforms as default, and also in the 32bit compatible
model on all platforms including x86.  It's been implemented already
over a decade, so we can say it's fairly safe and stably working.

With the help of the knowledge above, this patch introduces a new PCM
info flag SNDRV_PCM_INFO_SYNC_APPLPTR for achieving the appl_ptr sync
from user-space.  When a driver sets this flag at open, the PCM status
/ control mmap is disabled, which effectively switches to SYNC_PTR
mode in user-space side.

In this version, both PCM status and control mmaps are disabled
although only the latter, control mmap, is the target.  It's because
the current alsa-lib implementation supposes that both status and
control mmaps are always coupled, thus it handles a fatal error when
only one of them fails.

Of course, the disablement of the status/control mmaps may bring a
slight performance overhead.  Thus, as of now, this should be used
only for the dedicated devices that deserves.

Note that the disablement of mmap is a sort of workaround.  In the
later patch, we'll introduce the way to identify the protocol version
alsa-lib supports, and keep mmap working while the sync_ptr is
performed together.

Reviewed-by: Takashi Sakamoto &lt;o-takashi@sakamocchi.jp&gt;
Signed-off-by: Takashi Iwai &lt;tiwai@suse.de&gt;
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