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r: 56528
b: refs/heads/master
c: 83c6590
h: refs/heads/master
v: v3
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David Brownell authored and Linus Torvalds committed May 17, 2007
1 parent 78434bd commit 0e63cde
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2 changes: 1 addition & 1 deletion [refs]
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refs/heads/master: 621e59a771f310358ade8f14cb745d5d5f1c410e
refs/heads/master: 83c6590cb83d3106df12fee36ac2a261951b8c88
8 changes: 6 additions & 2 deletions trunk/Documentation/gpio.txt
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Expand Up @@ -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.
Expand Down Expand Up @@ -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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