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Date:   Tue, 17 Sep 2019 10:06:13 +0300
From:   Dan Carpenter <dan.carpenter@oracle.com>
To:     Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Cc:     Maxime Ripard <mripard@kernel.org>, mchehab@kernel.org,
        linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
        kernel-janitors@vger.kernel.org
Subject: Re: [PATCH] media: v4l: cadence: Fix how unsued lanes are handled in
 'csi2rx_start()'
Message-ID: <20190917070613.GA2959@kadam>
References: <20190912204450.17625-1-christophe.jaillet@wanadoo.fr>
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 <20190916062846.GD18977@kadam>
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On Mon, Sep 16, 2019 at 09:24:26PM +0200, Christophe JAILLET wrote:
> Le 16/09/2019 ? 08:28, Dan Carpenter a ?crit?:
> > On Fri, Sep 13, 2019 at 09:57:09AM +0200, Maxime Ripard wrote:
> > > Hi Christophe,
> > > 
> > > On Thu, Sep 12, 2019 at 10:44:50PM +0200, Christophe JAILLET wrote:
> > > > The 2nd parameter of 'find_first_zero_bit()' is a number of bits, not of
> > > > bytes. So use 'BITS_PER_LONG' instead of 'sizeof(lanes_used)'.
> > > > 
> > > > Fixes: 1fc3b37f34f6 ("media: v4l: cadence: Add Cadence MIPI-CSI2 RX driver")
> > > > Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> > > > ---
> > > > This patch is purely speculative. Using BITS_PER_LONG looks logical to me,
> > > > but I'm not 100% sure that it is what is expected here. 'csi2rx->max_lanes'
> > > > could also be a good candidate.
> > > Yeah, csi2rx->max_lanes would make more sense in that context. Could
> > > you resend a new version?
> > This is sort of unrelated, but for Smatch purposes the csi2rx->max_lanes
> > comes from the firmware in csi2rx_parse_dt() and it could be any u8
> > value.
> 
> Hi Dan,
> 
> not sure to follow you.
> 
> csi2rx_probe()
> ? --> csi2rx_get_resources()
> ? ?? -->? ...
> ??? ????? dev_cfg = readl(csi2rx->base + CSI2RX_DEVICE_CFG_REG);
> ??? ??? ? ...
> ??? ????? csi2rx->max_lanes = dev_cfg & 7;
> ????????? if (csi2rx->max_lanes > CSI2RX_LANES_MAX) {
> ??? ?? ? ? ? dev_err(&pdev->dev, "Invalid number of lanes: %u\n",
> ??? ??? ?? ? ? ? ? ? csi2rx->max_lanes);
> ? ? ? ?? ??? return -EINVAL;
> ????????? }
> 
> So I guess, that we can trust max_lanes because of the 'if (... >
> CSI2RX_LANES_MAX)' check.
> 
> Did I miss something?

Ugh...  I was looking at ->num_lanes and I was also just totally wrong.
Smatch parses that badly.  Smatch actually parses ->max_lanes correctly
though so that's ok.

Sorry for the noise on this.

regards,
dan carpenter