forked from luck/tmp_suning_uos_patched
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: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -111,7 +111,9 @@ setting up a platform_device using the GPIO, is mark its direction:
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The return value is zero for success, else a negative errno. It should
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be checked, since the get/set calls don't have error returns and since
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misconfiguration is possible. (These calls could sleep.)
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misconfiguration is possible. You should normally issue these calls from
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a task context. However, for spinlock-safe GPIOs it's OK to use them
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before tasking is enabled, as part of early board setup.
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For output GPIOs, the value provided becomes the initial output value.
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This helps avoid signal glitching during system startup.
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@ -197,7 +199,9 @@ However, many platforms don't currently support this mechanism.
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Passing invalid GPIO numbers to gpio_request() will fail, as will requesting
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GPIOs that have already been claimed with that call. The return value of
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gpio_request() must be checked. (These calls could sleep.)
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gpio_request() must be checked. You should normally issue these calls from
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a task context. However, for spinlock-safe GPIOs it's OK to request GPIOs
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before tasking is enabled, as part of early board setup.
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These calls serve two basic purposes. One is marking the signals which
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are actually in use as GPIOs, for better diagnostics; systems may have
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