linux-kernel - Re: [PATCH] drm/bridge: parade-ps8640: check return values in ps8640_aux

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Message-ID: <YU5xGn6i2a7vjajI@shinobu>
Date:   Sat, 25 Sep 2021 09:45:14 +0900
From:   William Breathitt Gray <vilhelm.gray@...il.com>
To:     Tim Gardner <tim.gardner@...onical.com>
Cc:     dri-devel@...ts.freedesktop.org,
        Syed Nayyar Waris <syednwaris@...il.com>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Robert Foss <robert.foss@...aro.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/bridge: parade-ps8640: check return values in
 ps8640_aux_transfer()

On Fri, Sep 24, 2021 at 10:03:27AM -0600, Tim Gardner wrote:
> 
> 
> On 9/24/21 9:26 AM, Tim Gardner wrote:
> > Coverity complains of an unused return code:
> > 
> > CID 120459 (#1 of 1): Unchecked return value (CHECKED_RETURN)
> > 7. check_return: Calling regmap_bulk_write without checking return value (as is
> > done elsewhere 199 out of 291 times).
> > 204        regmap_bulk_write(map, PAGE0_SWAUX_ADDR_7_0, addr_len,
> > 205                          ARRAY_SIZE(addr_len));
> > 
> > While I was at it I noticed 2 other places where return codes were not being
> > used, or used incorrectly (which is a real bug).
> > 
> > Fix these errors by correctly using the returned error codes.
> > 
> > Cc: William Breathitt Gray <vilhelm.gray@...il.com>
> > Cc: Syed Nayyar Waris <syednwaris@...il.com>
> > Cc: Andrzej Hajda <a.hajda@...sung.com>
> > Cc: Neil Armstrong <narmstrong@...libre.com>
> > Cc: Robert Foss <robert.foss@...aro.org>
> > Cc: Laurent Pinchart <Laurent.pinchart@...asonboard.com>
> > Cc: Jonas Karlman <jonas@...boo.se>
> > Cc: Jernej Skrabec <jernej.skrabec@...il.com>
> > Cc: David Airlie <airlied@...ux.ie>
> > Cc: Daniel Vetter <daniel@...ll.ch>
> > Cc: linux-iio@...r.kernel.org
> > Cc: linux-kernel@...r.kernel.org
> > Cc: dri-devel@...ts.freedesktop.org
> > Signed-off-by: Tim Gardner <tim.gardner@...onical.com>
> > ---
> >   drivers/gpu/drm/bridge/parade-ps8640.c | 14 +++++++++++---
> >   1 file changed, 11 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c
> > index 3aaa90913bf8..591da962970a 100644
> > --- a/drivers/gpu/drm/bridge/parade-ps8640.c
> > +++ b/drivers/gpu/drm/bridge/parade-ps8640.c
> > @@ -201,8 +201,12 @@ static ssize_t ps8640_aux_transfer(struct drm_dp_aux *aux,
> >   	addr_len[PAGE0_SWAUX_LENGTH - base] = (len == 0) ? SWAUX_NO_PAYLOAD :
> >   					      ((len - 1) & SWAUX_LENGTH_MASK);
> >   
> > -	regmap_bulk_write(map, PAGE0_SWAUX_ADDR_7_0, addr_len,
> > +	ret = regmap_bulk_write(map, PAGE0_SWAUX_ADDR_7_0, addr_len,
> >   			  ARRAY_SIZE(addr_len));
> > +	if (ret) {
> > +		DRM_DEV_ERROR(dev, "failed to bulk write ADDR_7_0: %d\n", ret);
> > +		return ret;
> > +	}
> >   
> >   	if (len && (request == DP_AUX_NATIVE_WRITE ||
> >   		    request == DP_AUX_I2C_WRITE)) {
> > @@ -218,13 +222,17 @@ static ssize_t ps8640_aux_transfer(struct drm_dp_aux *aux,
> >   		}
> >   	}
> >   
> > -	regmap_write(map, PAGE0_SWAUX_CTRL, SWAUX_SEND);
> > +	ret = regmap_write(map, PAGE0_SWAUX_CTRL, SWAUX_SEND);
> > +	if (ret) {
> > +		DRM_DEV_ERROR(dev, "failed to write SEND: %d\n", ret);
> > +		return ret;
> > +	}
> >   
> >   	/* Zero delay loop because i2c transactions are slow already */
> >   	regmap_read_poll_timeout(map, PAGE0_SWAUX_CTRL, data,
> >   				 !(data & SWAUX_SEND), 0, 50 * 1000);
> >   
> > -	regmap_read(map, PAGE0_SWAUX_STATUS, &data);
> > +	ret = regmap_read(map, PAGE0_SWAUX_STATUS, &data);
> >   	if (ret) {
> >   		DRM_DEV_ERROR(dev, "failed to read PAGE0_SWAUX_STATUS: %d\n",
> >   			      ret);
> > 
> 
> I forgot to mention this patch is for linux-next next-20210924.
> 
> -----------
> Tim Gardner
> Canonical, Inc

Hi Tim,

For future patches, the git format-patch command has a useful option
'--base'. It will allow you to provide the base tree information for
users and maintainers so that they know where to apply the patch:
https://git-scm.com/docs/git-format-patch#_base_tree_information

Sincerely,

William Breathitt Gray

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