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Message-ID: <f67787da-dc1c-3e05-c1e2-e8737641dfd0@wanadoo.fr>
Date: Mon, 16 Sep 2019 21:24:26 +0200
From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
To: Dan Carpenter <dan.carpenter@...cle.com>,
Maxime Ripard <mripard@...nel.org>
Cc: mchehab@...nel.org, linux-media@...r.kernel.org,
linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] media: v4l: cadence: Fix how unsued lanes are handled in
'csi2rx_start()'
Le 16/09/2019 à 08:28, Dan Carpenter a écrit :
> 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@...adoo.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?
> I sort of wish that people would write code which was known to be
> correct just from reading the kernel code, without looking at the
> firmware... I guess I could mark v4l2_fwnode_endpoint_parse() as always
> giving us valid data, but that still wouldn't tell us what the valid
> data is. It's hard to know the right answer from a static analysis
> point of view.
>
> regards,
> dan carpenter
>
>
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