linux-kernel - Re: [PATCH v3 2/2] drm/tiny: Add driver for Sharp Memory LCD

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Message-ID: <darls2mffvsw2ktkirzimzij6w5w45hxylvfcfwgmd3k3elmar@xeg6mfpa3yax>
Date: Mon, 29 Jul 2024 08:05:47 -0400
From: Alex Lanzano <lanzano.alex@...il.com>
To: Markus Elfring <Markus.Elfring@....de>
Cc: Mehdi Djait <mehdi.djait@...tlin.com>, dri-devel@...ts.freedesktop.org, 
	devicetree@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>, 
	Christophe Jaillet <christophe.jaillet@...adoo.fr>, Conor Dooley <conor+dt@...nel.org>, 
	Daniel Vetter <daniel@...ll.ch>, David Airlie <airlied@...il.com>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Maxime Ripard <mripard@...nel.org>, Rob Herring <robh@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>
Subject: Re: [PATCH v3 2/2] drm/tiny: Add driver for Sharp Memory LCD

On Mon, Jul 29, 2024 at 01:00:47PM GMT, Markus Elfring wrote:
> …
> > +++ b/drivers/gpu/drm/tiny/sharp-memory.c
> > @@ -0,0 +1,684 @@
> …
> > static int sharp_memory_update_display(struct sharp_memory_device *smd,
> > +				       struct drm_framebuffer *fb,
> > +				       struct drm_rect clip,
> > +				       struct drm_format_conv_state *fmtcnv_state)
> > +{
> …
> > +	mutex_lock(&smd->tx_mutex);
> > +
> > +	/* Populate the transmit buffer with frame data */
> …
> > +	mutex_unlock(&smd->tx_mutex);
> > +
> > +	return ret;
> > +}
> …
> 
> Under which circumstances would you become interested to apply a statement
> like “guard(mutex)(&smd->tx_mutex);”?
> https://elixir.bootlin.com/linux/v6.10.2/source/include/linux/mutex.h#L196
> 

Ah, I didn't realize guarded mutexes were implemented. That's really
good to know.

I'd usually use them when it's possible to return before mutex_unlock is
called to avoid goto cleanup logic. But it's probably best to just use them
by default.

Thanks for the review. Will clean up in v4.

Best regards,
Alex