linux-toradex.git/drivers/gpio/gpiolib.c, branch v2.6.27.20

gpiolib: extend gpio label column width in debugfs file

2008-12-05T18:55:11+00:00

commit 6e8ba729b6332f2a75572e02480936d2b51665aa upstream.

There are already various drivers having bigger label than 12 bytes.  Most
of them fit well under 20 bytes but make column width exact so that
oversized labels don't mess up output alignment.

Signed-off-by: Jarkko Nikula 
Acked-by: David Brownell 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

gpiolib: fix oops in gpio_get_value_cansleep()

2008-10-25T21:32:36+00:00

commit 978ccaa8ea5d8c7bf6b676209f2fc126eae6355b upstream

We can get the following oops from gpio_get_value_cansleep() when a GPIO
controller doesn't provide a get() callback:

 Unable to handle kernel paging request for instruction fetch
 Faulting instruction address: 0x00000000
 Oops: Kernel access of bad area, sig: 11 [#1]
 [...]
 NIP [00000000] 0x0
 LR [c0182fb0] gpio_get_value_cansleep+0x40/0x50
 Call Trace:
 [c7b79e80] [c0183f28] gpio_value_show+0x5c/0x94
 [c7b79ea0] [c01a584c] dev_attr_show+0x30/0x7c
 [c7b79eb0] [c00d6b48] fill_read_buffer+0x68/0xe0
 [c7b79ed0] [c00d6c54] sysfs_read_file+0x94/0xbc
 [c7b79ef0] [c008f24c] vfs_read+0xb4/0x16c
 [c7b79f10] [c008f580] sys_read+0x4c/0x90
 [c7b79f40] [c0013a14] ret_from_syscall+0x0/0x38

It's OK to request the value of *any* GPIO; most GPIOs are bidirectional,
so configuring them as outputs just enables an output driver and doesn't
disable the input logic.

So the problem is that gpio_get_value_cansleep() isn't making the same
sanity check that gpio_get_value() does: making sure this GPIO isn't one
of the atypical "no input logic" cases.

Reported-by: Anton Vorontsov 
Signed-off-by: David Brownell 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

gpio: sysfs interface

2008-07-25T17:53:30+00:00

This adds a simple sysfs interface for GPIOs.

    /sys/class/gpio
    	/export ... asks the kernel to export a GPIO to userspace
    	/unexport ... to return a GPIO to the kernel
        /gpioN ... for each exported GPIO #N
	    /value ... always readable, writes fail for input GPIOs
	    /direction ... r/w as: in, out (default low); write high, low
	/gpiochipN ... for each gpiochip; #N is its first GPIO
	    /base ... (r/o) same as N
	    /label ... (r/o) descriptive, not necessarily unique
	    /ngpio ... (r/o) number of GPIOs; numbered N .. N+(ngpio - 1)

GPIOs claimed by kernel code may be exported by its owner using a new
gpio_export() call, which should be most useful for driver debugging.
Such exports may optionally be done without a "direction" attribute.

Userspace may ask to take over a GPIO by writing to a sysfs control file,
helping to cope with incomplete board support or other "one-off"
requirements that don't merit full kernel support:

  echo 23 > /sys/class/gpio/export
	... will gpio_request(23, "sysfs") and gpio_export(23);
	use /sys/class/gpio/gpio-23/direction to (re)configure it,
	when that GPIO can be used as both input and output.
  echo 23 > /sys/class/gpio/unexport
	... will gpio_free(23), when it was exported as above

The extra D-space footprint is a few hundred bytes, except for the sysfs
resources associated with each exported GPIO.  The additional I-space
footprint is about two thirds of the current size of gpiolib (!).  Since
no /dev node creation is involved, no "udev" support is needed.

Related changes:

  * This adds a device pointer to "struct gpio_chip".  When GPIO
    providers initialize that, sysfs gpio class devices become children of
    that device instead of being "virtual" devices.

  * The (few) gpio_chip providers which have such a device node have
    been updated.

  * Some gpio_chip drivers also needed to update their module "owner"
    field ...  for which missing kerneldoc was added.

  * Some gpio_chips don't support input GPIOs.  Those GPIOs are now
    flagged appropriately when the chip is registered.

Based on previous patches, and discussion both on and off LKML.

A Documentation/ABI/testing/sysfs-gpio update is ready to submit once this
merges to mainline.

[akpm@linux-foundation.org: a few maintenance build fixes]
Signed-off-by: David Brownell 
Cc: Guennadi Liakhovetski 
Cc: Greg KH 
Cc: Kay Sievers 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

gpiolib: fix off by one errors

2008-05-24T16:56:11+00:00

The last gpio belonging to a chip is chip->base + chip->ngpios - 1.  Some
places in the code, but not all, forgot the critical minus one.

Signed-off-by: Trent Piepho 
Acked-by: David Brownell 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

drivers: replace remaining FUNCTION occurrences

2008-04-30T15:29:53+00:00

__FUNCTION__ is gcc-specific, use __func__

Signed-off-by: Harvey Harrison 
Cc: Ben Dooks 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

gpiochip_reserve()

2008-04-28T15:58:34+00:00

Add a new function gpiochip_reserve() to reserve ranges of gpios that platform
code has pre-allocated.  That is, this marks gpio numbers which will be
claimed by drivers that haven't yet been loaded, and thus are not available
for dynamic gpio number allocation.

[akpm@linux-foundation.org: remove unneeded __must_check]
[david-b@pacbell.net: don't export gpiochip_reserve (section fix)]
Signed-off-by: Anton Vorontsov 
Signed-off-by: David Brownell 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

gpiolib: dynamic gpio number allocation

2008-04-28T15:58:34+00:00

If gpio_chip->base is negative during registration, gpiolib performs dynamic
base allocation.  This is useful for devices that aren't always present, such
as GPIOs on hotplugged devices rather than mainboards.  (This behavior was
previously specified but not implemented.)

To avoid using any numbers that may have been explicitly assigned but not yet
registered, this dynamic allocation assigns GPIO numbers from the biggest
number on down, instead of from the smallest on up.

Signed-off-by: Anton Vorontsov 
Signed-off-by: David Brownell 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

gpio: define gpio_is_valid()

2008-04-28T15:58:34+00:00

Introduce a gpio_is_valid() predicate; use it in gpiolib.

Signed-off-by: Guennadi Liakhovetski 
    [ use inline function; follow the gpio_* naming convention;
      work without gpiolib; all programming interfaces need docs ]
Signed-off-by: David Brownell 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

gpiolib: better rmmod infrastructure

2008-04-28T15:58:34+00:00

As long as one or more GPIOs on a gpio chip are used its driver should not be
unloaded.  The existing mechanism (gpiochip_remove failure) doesn't address
that, since rmmod can no longer be made to fail by having the cleanup code
report errors.  Module usecounts are the solution.

Assuming standard "initialize struct to zero" policies, this change won't
affect SOC platform drivers.  However, drivers for external chips (on I2C and
SPI busses) should be updated if they can be built as modules.

Signed-off-by: Guennadi Liakhovetski 
[ gpio_ensure_requested() needs to update module usecounts too ]
Signed-off-by: David Brownell 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

gpiolib: add gpio provider infrastructure

2008-02-05T17:44:12+00:00

Provide new implementation infrastructure that platforms may choose to use
when implementing the GPIO programming interface.  Platforms can update their
GPIO support to use this.  In many cases the incremental cost to access a
non-inlined GPIO should be less than a dozen instructions, with the memory
cost being about a page (total) of extra data and code.  The upside is:

  * Providing two features which were "want to have (but OK to defer)" when
    GPIO interfaces were first discussed in November 2006:

    -	A "struct gpio_chip" to plug in GPIOs that aren't directly supported
	by SOC platforms, but come from FPGAs or other multifunction devices
	using conventional device registers (like UCB-1x00 or SM501 GPIOs,
	and southbridges in PCs with more open specs than usual).

    -	Full support for message-based GPIO expanders, where registers are
	accessed through sleeping I/O calls.  Previous support for these
	"cansleep" calls was just stubs.  (One example: the widely used
	pcf8574 I2C chips, with 8 GPIOs each.)

  * Including a non-stub implementation of the gpio_{request,free}() calls,
    making those calls much more useful.  The diagnostic labels are also
    recorded given DEBUG_FS, so /sys/kernel/debug/gpio can show a snapshot
    of all GPIOs known to this infrastructure.

The driver programming interfaces introduced in 2.6.21 do not change at all;
this infrastructure is entirely below those covers.

Signed-off-by: David Brownell 
Cc: Sam Ravnborg 
Cc: Jean Delvare 
Cc: Eric Miao 
Cc: Haavard Skinnemoen 
Cc: Philipp Zabel 
Cc: Russell King 
Cc: Ben Gardner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

linux-toradex.git/drivers/gpio/gpiolib.c, branch v2.6.27.20

gpiolib: extend gpio label column width in debugfs file

gpiolib: fix oops in gpio_get_value_cansleep()

gpio: sysfs interface

gpiolib: fix off by one errors

drivers: replace remaining __FUNCTION__ occurrences

gpiochip_reserve()

gpiolib: dynamic gpio number allocation

gpio: define gpio_is_valid()

gpiolib: better rmmod infrastructure

gpiolib: add gpio provider infrastructure

drivers: replace remaining FUNCTION occurrences