linux-kernel - Re: [PATCH v2 30/36] media: imx: Fix misuse of min_buffers

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <fc0baa11373888c3dc09e76fbbbb6d382028d738.camel@pengutronix.de>
Date:   Mon, 04 Dec 2023 14:52:32 +0100
From:   Philipp Zabel <p.zabel@...gutronix.de>
To:     Benjamin Gaignard <benjamin.gaignard@...labora.com>,
        hverkuil@...all.nl, mchehab@...nel.org, tfiga@...omium.org,
        m.szyprowski@...sung.com, matt.ranostay@...sulko.com
Cc:     linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
        linux-staging@...ts.linux.dev, kernel@...labora.com,
        Steve Longerbeam <slongerbeam@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>
Subject: Re: [PATCH v2 30/36] media: imx: Fix misuse of min_buffers_needed
 field

Hi Benjamin,

On Mo, 2023-12-04 at 14:23 +0100, Benjamin Gaignard wrote:
> 'min_buffers_needed' is suppose to be used to indicate the number
> of buffers needed by DMA engine to start streaming.
> imx-media-capture driver doesn't use DMA engine and just want to specify
> the minimum number of buffers to allocate when calling VIDIOC_REQBUFS.

This is used by imx-media-csi and imx-ic-prpencvf. Both expect two
buffers to setup the IDMAC DMA engine double buffer (see
csi_idmac_setup_vb2_buf()/prp_setup_vb2_buf()).

These functions can cope with less than two buffers queued, by using a
special "underrun" buffer as a workaround, but the hardware does
require two buffer addresses, so I'm not sure whether this really
should be called a misuse of min_buffers_needed.

regards
Philipp