linux-kernel - Re: [PATCH v2 04/35] brcmfmac: firmware: Support having multiple alt paths

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Message-ID: <8394dbcd-f500-b1ae-fcd8-15485d8c0888@gmail.com>
Date:   Wed, 5 Jan 2022 01:09:45 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Hector Martin <marcan@...can.st>,
        Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Arend van Spriel <aspriel@...il.com>,
        Franky Lin <franky.lin@...adcom.com>,
        Hante Meuleman <hante.meuleman@...adcom.com>,
        Chi-hsien Lin <chi-hsien.lin@...ineon.com>,
        Wright Feng <wright.feng@...ineon.com>
Cc:     Sven Peter <sven@...npeter.dev>,
        Alyssa Rosenzweig <alyssa@...enzweig.io>,
        Mark Kettenis <kettenis@...nbsd.org>,
        Rafał Miłecki <zajec5@...il.com>,
        Pieter-Paul Giesberts <pieter-paul.giesberts@...adcom.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Hans de Goede <hdegoede@...hat.com>,
        "John W. Linville" <linville@...driver.com>,
        "brian m. carlson" <sandals@...stytoothpaste.net>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-acpi@...r.kernel.org, brcm80211-dev-list.pdl@...adcom.com,
        SHA-cyfmac-dev-list@...ineon.com
Subject: Re: [PATCH v2 04/35] brcmfmac: firmware: Support having multiple alt
 paths

04.01.2022 11:43, Hector Martin пишет:
>>> +static int brcm_alt_fw_paths(const char *path, const char *board_type,
>>> +			     const char *alt_paths[BRCMF_FW_MAX_ALT_PATHS])>  {
>>>  	char alt_path[BRCMF_FW_NAME_LEN];
>>>  	const char *suffix;
>>>  
>>> +	memset(alt_paths, 0, array_size(sizeof(*alt_paths),
>>> +					BRCMF_FW_MAX_ALT_PATHS));
>> You don't need to use array_size() since size of a fixed array is
>> already known.
>>
>> memset(alt_paths, 0, sizeof(alt_paths));
> It's a function argument, so that doesn't work and actually throws a
> warning. Array function argument notation is informative only; they
> behave strictly equivalent to pointers. Try it:
> 
> $ cat test.c
> #include <stdio.h>
> 
> void foo(char x[42])
> {
> 	printf("%ld\n", sizeof(x));
> }
> 
> int main() {
> 	char x[42];
> 
> 	foo(x);
> }
> $ gcc test.c
> test.c: In function ‘foo’:
> test.c:5:31: warning: ‘sizeof’ on array function parameter ‘x’ will
> return size of ‘char *’ [-Wsizeof-array-argument]
>     5 |         printf("%ld\n", sizeof(x));
>       |                               ^
> test.c:3:15: note: declared here
>     3 | void foo(char x[42])
>       |          ~~~~~^~~~~
> $ ./a.out
> 8

Then please use "const char **alt_paths" for the function argument to
make code cleaner and add another argument to pass the number of array
elements.

static int brcm_alt_fw_paths(const char *path, const char *board_type,
			     const char **alt_paths, unsigned int num_paths)
{
	size_t alt_paths_size = array_size(sizeof(*alt_paths), num_paths);
	
	memset(alt_paths, 0, alt_paths_size);
}

...

Maybe even better create a dedicated struct for the alt_paths:

struct brcmf_fw_alt_paths {
	const char *alt_paths[BRCMF_FW_MAX_ALT_PATHS];
	unsigned int index;
};

and then use the ".index" in the brcm_free_alt_fw_paths(). I suppose
this will make code a bit nicer and easier to follow.