linux-kernel - Re: [PATCH] clkdev: report over-sized strings when creating clkdev entries

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Message-ID: <ZkfYqj+OcAxd9O2t@shell.armlinux.org.uk>
Date: Fri, 17 May 2024 23:22:34 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Guenter Roeck <linux@...ck-us.net>
Cc: linux-arm-kernel@...ts.infradead.org,
	Duanqiang Wen <duanqiangwen@...-swift.com>, mturquette@...libre.com,
	sboyd@...nel.org, linux-clk@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] clkdev: report over-sized strings when creating clkdev
 entries

On Fri, May 17, 2024 at 03:09:12PM -0700, Guenter Roeck wrote:
> Hi,
> 
> On Fri, Mar 15, 2024 at 11:47:55AM +0000, Russell King (Oracle) wrote:
> > Report an error when an attempt to register a clkdev entry results in a
> > truncated string so the problem can be easily spotted.
> > 
> > Reported by: Duanqiang Wen <duanqiangwen@...-swift.com>
> > Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
> > Reviewed-by: Stephen Boyd <sboyd@...nel.org>
> 
> With this patch in the mainline kernel, I get
> 
> 10000000.clock-controller:corepll: device ID is greater than 24
> sifive-clk-prci 10000000.clock-controller: Failed to register clkdev for corepll: -12
> sifive-clk-prci 10000000.clock-controller: could not register clocks: -12
> sifive-clk-prci 10000000.clock-controller: probe with driver sifive-clk-prci failed with error -12
> ...
> platform 10060000.gpio: deferred probe pending: platform: supplier 10000000.clock-controller not ready
> platform 10010000.serial: deferred probe pending: platform: supplier 10000000.clock-controller not ready
> platform 10011000.serial: deferred probe pending: platform: supplier 10000000.clock-controller not ready
> platform 10040000.spi: deferred probe pending: platform: supplier 10000000.clock-controller not ready
> platform 10050000.spi: deferred probe pending: platform: supplier 10000000.clock-controller not ready
> platform 10090000.ethernet: deferred probe pending: platform: supplier 10000000.clock-controller not ready
> 
> when trying to boot sifive_u in qemu.
> 
> Apparently, "10000000.clock-controller" is too long. Any suggestion on
> how to solve the problem ? I guess using dev_name(dev) as dev_id parameter
> for clk_hw_register_clkdev() is not or no longer a good idea.
> What else should be used instead ?

It was *never* a good idea. clkdev uses a fixed buffer size of 20
characters including the NUL character, and "10000000.clock-controller"
would have been silently truncated to "10000000.clock-cont", and thus

                        if (!dev_id || strcmp(p->dev_id, dev_id))

would never have matched.

We need to think about (a) whether your use of clk_hw_register_clkdev()
is still appropriate, and (b) whether we need to increase the size of
the strings.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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