linux-kernel - Re: [PATCH v2 65/65] clk: Warn if we register a mux without determine

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>] [day] [month] [year] [list]

Message-ID: <20221107105653.GE10437@ediswmail.ad.cirrus.com>
Date:   Mon, 7 Nov 2022 10:56:53 +0000
From:   Charles Keepax <ckeepax@...nsource.cirrus.com>
To:     Maxime Ripard <maxime@...no.tech>
CC:     Stephen Boyd <sboyd@...nel.org>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Chen-Yu Tsai <wens@...e.org>, Daniel Vetter <daniel@...ll.ch>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jaroslav Kysela <perex@...ex.cz>,
        Shawn Guo <shawnguo@...nel.org>,
        Fabio Estevam <festevam@...il.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Claudiu Beznea <claudiu.beznea@...rochip.com>,
        Michael Turquette <mturquette@...libre.com>,
        Dinh Nguyen <dinguyen@...nel.org>,
        Paul Cercueil <paul@...pouillou.net>,
        Chunyan Zhang <zhang.lyra@...il.com>,
        Manivannan Sadhasivam <mani@...nel.org>,
        Andreas Färber <afaerber@...e.de>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Abel Vesa <abelvesa@...nel.org>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        Peter De Schrijver <pdeschrijver@...dia.com>,
        Orson Zhai <orsonzhai@...il.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Prashant Gaikwad <pgaikwad@...dia.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Samuel Holland <samuel@...lland.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Richard Fitzgerald <rf@...nsource.cirrus.com>,
        Vinod Koul <vkoul@...nel.org>,
        NXP Linux Team <linux-imx@....com>,
        Sekhar Nori <nsekhar@...com>,
        Kishon Vijay Abraham I <kishon@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Takashi Iwai <tiwai@...e.com>,
        David Airlie <airlied@...il.com>,
        Luca Ceresoli <luca.ceresoli@...tlin.com>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        David Lechner <david@...hnology.com>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Mark Brown <broonie@...nel.org>,
        Max Filippov <jcmvbkbc@...il.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <alsa-devel@...a-project.org>,
        <linux-mediatek@...ts.infradead.org>,
        <linux-phy@...ts.infradead.org>, <linux-mips@...r.kernel.org>,
        <linux-renesas-soc@...r.kernel.org>,
        <linux-actions@...ts.infradead.org>, <linux-clk@...r.kernel.org>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        <patches@...nsource.cirrus.com>, <linux-tegra@...r.kernel.org>,
        <linux-rtc@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-sunxi@...ts.linux.dev>, <linux-kernel@...r.kernel.org>,
        <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH v2 65/65] clk: Warn if we register a mux without
 determine_rate

On Fri, Nov 04, 2022 at 02:18:22PM +0100, Maxime Ripard wrote:
> The determine_rate hook allows to select the proper parent and its rate
> for a given clock configuration. On another hand, set_parent is there to
> change the parent of a mux.
> 
> Some clocks provide a set_parent hook but don't implement
> determine_rate. In such a case, set_parent is pretty much useless since
> the clock framework will always assume the current parent is to be used,
> and we will thus never change it.
> 
> This situation can be solved in two ways:
>   - either we don't need to change the parent, and we thus shouldn't
>     implement set_parent;
>   - or we don't want to change the parent, in this case we should set
>     CLK_SET_RATE_NO_REPARENT;
>   - or we're missing a determine_rate implementation.
> 
> The latter is probably just an oversight from the driver's author, and
> we should thus raise their awareness about the fact that the current
> state of the driver is confusing.
> 
> It's not clear at this point how many drivers are affected though, so
> let's make it a warning instead of an error for now.
> 

Commit message could probably use updated to make the new state
of the chain.

Thanks,
Charles