Commit 83c6590c authored by David Brownell's avatar David Brownell Committed by Linus Torvalds
Browse files

gpio interface loosens call restrictions 



Loosen gpio_{request,free}() and gpio_direction_{in,out}put() call context
restrictions slightly, so a common idiom is no longer an error: board init
code setting up spinlock-safe GPIOs before tasking is enabled.

The issue was caught by some paranoid code with might_sleep() checks.  The
legacy platform-specific GPIO interfaces stick to spinlock-safe GPIOs, so this
change reflects current implementations and won't break anything.

Signed-off-by: default avatarDavid Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 621e59a7

Documentation/gpio.txt

+6 −2
Original line number Diff line number Diff line
@@ -111,7 +111,9 @@ setting up a platform_device using the GPIO, is mark its direction: 


The return value is zero for success, else a negative errno.  It should

be checked, since the get/set calls don't have error returns and since

misconfiguration is possible.  (These calls could sleep.)

misconfiguration is possible.  You should normally issue these calls from

a task context.  However, for spinlock-safe GPIOs it's OK to use them

before tasking is enabled, as part of early board setup.



For output GPIOs, the value provided becomes the initial output value.

This helps avoid signal glitching during system startup.
@@ -197,7 +199,9 @@ However, many platforms don't currently support this mechanism. 


Passing invalid GPIO numbers to gpio_request() will fail, as will requesting

GPIOs that have already been claimed with that call.  The return value of

gpio_request() must be checked.  (These calls could sleep.)

gpio_request() must be checked.  You should normally issue these calls from

a task context.  However, for spinlock-safe GPIOs it's OK to request GPIOs

before tasking is enabled, as part of early board setup.



These calls serve two basic purposes.  One is marking the signals which

are actually in use as GPIOs, for better diagnostics; systems may have

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