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authorJames Bottomley <jejb@mulgrave.il.steeleye.com>2007-05-30 23:57:05 -0500
committerJames Bottomley <jejb@mulgrave.il.steeleye.com>2007-05-30 23:57:05 -0500
commit5bc65793cbf8da0d35f19ef025dda22887e79e80 (patch)
tree8291998abd73055de6f487fafa174ee2a5d3afee /Documentation/gpio.txt
parent6edae708bf77e012d855a7e2c7766f211d234f4f (diff)
parent3f0a6766e0cc5a577805732e5adb50a585c58175 (diff)
[SCSI] Merge up to linux-2.6 head
Conflicts: drivers/scsi/jazz_esp.c Same changes made by both SCSI and SPARC trees: problem with UTF-8 conversion in the copyright. Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
Diffstat (limited to 'Documentation/gpio.txt')
-rw-r--r--Documentation/gpio.txt8
1 files changed, 6 insertions, 2 deletions
diff --git a/Documentation/gpio.txt b/Documentation/gpio.txt
index e8be0abb346..36af58eba13 100644
--- a/Documentation/gpio.txt
+++ b/Documentation/gpio.txt
@@ -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