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backlight: Fix external uses of backlight internal semaphore

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backlight_device->sem has a very specific use as documented in the
header file. The external users of this are using it for a different
reason, to serialise access to the update_status() method.

backlight users were supposed to implement their own internal
serialisation of update_status() if needed but everyone is doing
things differently and incorrectly. Therefore add a global mutex to
take care of serialisation for everyone, once and for all.

Locking for get_brightness remains optional since most users don't
need it.

Also update the lcd class in a similar way.

Signed-off-by: Richard Purdie <rpurdie@rpsys.net>
This commit is contained in:
Richard Purdie
2007-02-08 22:25:09 +00:00
parent a8db3c1948
commit 28ee086d5b
15 changed files with 76 additions and 76 deletions
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19
arch/powerpc/platforms/powermac/backlight.c
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@@ -37,7 +37,9 @@ static int pmac_backlight_set_legacy_queued;
*/
static atomic_t kernel_backlight_disabled = ATOMIC_INIT(0);
/* Protect the pmac_backlight variable */
/* Protect the pmac_backlight variable below.
You should hold this lock when using the pmac_backlight pointer to
prevent its potential removal. */
DEFINE_MUTEX(pmac_backlight_mutex);
/* Main backlight storage
@@ -49,9 +51,6 @@ DEFINE_MUTEX(pmac_backlight_mutex);
* internal display, it doesn't matter. Other backlight drivers can be used
* independently.
*
* Lock ordering:
* pmac_backlight_mutex (global, main backlight)
* pmac_backlight->sem (backlight class)
*/
struct backlight_device *pmac_backlight;
@@ -104,7 +103,6 @@ static void pmac_backlight_key_worker(struct work_struct *work)
struct backlight_properties *props;
int brightness;
down(&pmac_backlight->sem);
props = pmac_backlight->props;
brightness = props->brightness +
@@ -117,9 +115,7 @@ static void pmac_backlight_key_worker(struct work_struct *work)
brightness = props->max_brightness;
props->brightness = brightness;
props->update_status(pmac_backlight);
up(&pmac_backlight->sem);
backlight_update_status(pmac_backlight);
}
mutex_unlock(&pmac_backlight_mutex);
}
@@ -145,7 +141,6 @@ static int __pmac_backlight_set_legacy_brightness(int brightness)
if (pmac_backlight) {
struct backlight_properties *props;
down(&pmac_backlight->sem);
props = pmac_backlight->props;
props->brightness = brightness *
(props->max_brightness + 1) /
@@ -156,8 +151,7 @@ static int __pmac_backlight_set_legacy_brightness(int brightness)
else if (props->brightness < 0)
props->brightness = 0;
props->update_status(pmac_backlight);
up(&pmac_backlight->sem);
backlight_update_status(pmac_backlight);
error = 0;
}
@@ -196,14 +190,11 @@ int pmac_backlight_get_legacy_brightness()
if (pmac_backlight) {
struct backlight_properties *props;
down(&pmac_backlight->sem);
props = pmac_backlight->props;
result = props->brightness *
(OLD_BACKLIGHT_MAX + 1) /
(props->max_brightness + 1);
up(&pmac_backlight->sem);
}
mutex_unlock(&pmac_backlight_mutex);