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

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Date: Fri, 17 May 2024 16:34:06 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
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 5/17/24 15:22, Russell King (Oracle) wrote:
> 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.
>

It isn't _my_ use, really. I only run a variety of boot tests with qemu.
I expect we'll see reports from others trying to boot the mainline kernel
on real sifive_u hardware or other hardware using the same driver or other
drivers using dev_name() as dev_id parameter. Coccinelle finds the
following callers:

/sound/soc/codecs/rt5682s.c: dev_name() used as dev_id at line 2833
/drivers/clk/sifive/sifive-prci.c: dev_name() used as dev_id at line 540
/sound/soc/codecs/tlv320aic32x4-clk.c: dev_name() used as dev_id at line 475
/drivers/i2c/busses/i2c-bcm2835.c: dev_name() used as dev_id at line 189
/sound/soc/codecs/rt5682.c: dev_name() used as dev_id at line 2909

Guenter