[PATCH] drm/xe/display: check for error on drmm_mutex_init

[Murthy, Arun R]

> -----Original Message-----
> From: De Marchi, Lucas <lucas.demarchi at intel.com>
> Sent: Wednesday, March 20, 2024 6:06 AM
> To: Murthy, Arun R <arun.r.murthy at intel.com>
> Cc: intel-gfx at lists.freedesktop.org; intel-xe at lists.freedesktop.org
> Subject: Re: [PATCH] drm/xe/display: check for error on drmm_mutex_init
> 
> On Tue, Mar 19, 2024 at 08:33:41AM +0530, Arun R Murthy wrote:
> >Check return value for drmm_mutex_init as it can fail and return on
> >failure.
> >
> >Signed-off-by: Arun R Murthy <arun.r.murthy at intel.com>
> >---
> > drivers/gpu/drm/xe/display/xe_display.c | 24 ++++++++++++++++++------
> > 1 file changed, 18 insertions(+), 6 deletions(-)
> >
> >diff --git a/drivers/gpu/drm/xe/display/xe_display.c
> >b/drivers/gpu/drm/xe/display/xe_display.c
> >index e4db069f0db3..c59fa832758d 100644
> >--- a/drivers/gpu/drm/xe/display/xe_display.c
> >+++ b/drivers/gpu/drm/xe/display/xe_display.c
> >@@ -107,12 +107,24 @@ int xe_display_create(struct xe_device *xe)
> >
> > 	xe->display.hotplug.dp_wq = alloc_ordered_workqueue("xe-dp", 0);
> >
> >-	drmm_mutex_init(&xe->drm, &xe->sb_lock);
> >-	drmm_mutex_init(&xe->drm, &xe->display.backlight.lock);
> >-	drmm_mutex_init(&xe->drm, &xe->display.audio.mutex);
> >-	drmm_mutex_init(&xe->drm, &xe->display.wm.wm_mutex);
> >-	drmm_mutex_init(&xe->drm, &xe->display.pps.mutex);
> >-	drmm_mutex_init(&xe->drm, &xe->display.hdcp.hdcp_mutex);
> >+	err = drmm_mutex_init(&xe->drm, &xe->sb_lock);
> >+	if (err)
> >+		return err;
> >+	err = drmm_mutex_init(&xe->drm, &xe->display.backlight.lock);
> >+	if (err)
> >+		return err;
> >+	err = drmm_mutex_init(&xe->drm, &xe->display.audio.mutex);
> >+	if (err)
> >+		return err;
> >+	err = drmm_mutex_init(&xe->drm, &xe->display.wm.wm_mutex);
> >+	if (err)
> >+		return err;
> >+	err = drmm_mutex_init(&xe->drm, &xe->display.pps.mutex);
> >+	if (err)
> >+		return err;
> >+	err = drmm_mutex_init(&xe->drm, &xe->display.hdcp.hdcp_mutex);
> >+	if (err)
> >+		return err;
> 
> 
> humn... but not very pretty. What about?
> 
> 	if ((err = drmm_mutex_init(&xe->drm, &xe->sb_lock)) ||
> 	    (err = drmm_mutex_init(&xe->drm, &xe->display.backlight.lock)) ||
> 	    (err = ...))
> 		return err;
> 
> I think there are few places in life for assignment + check in single statement,
> but IMO this is one of them where the alternative is uglier and more error
> prone.
> 
> thoughts?
> 

We should not proceed with the remaining mutex_init in case of failures. As an alternative we can have 
drmm_mutex_init(var1) ? (drmm_mutex_init(var2) ? drmm_mutex_init(var3) : return ret) : return ret;

With the existing one traversing the code is more easier, these optimization might make the code look complex.

Thanks and Regards,
Arun R Murthy
--------------------
> Lucas De Marchi
> 
> > 	xe->enabled_irq_mask = ~0;
> >
> > 	err = drmm_add_action_or_reset(&xe->drm, display_destroy, NULL);
> >--
> >2.25.1
> >