Re: [PATCH 3/3] firmware loader: allow distribution to choose default search paths

[Takashi Iwai <tiwai@suse.de>]

At Wed,  5 Jun 2013 13:42:49 +0800,
Ming Lei wrote:
> 
> For some distributions(e.g. android), firmware images aren't put
> under kernel built-in search paths, so introduce one Kconfig
> option to allow distributions or users to choose its specific default
> search paths, which are always tried before searching from kernel
> built-in paths in direct loading.
> 
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: Takashi Iwai <tiwai@suse.de>
> Signed-off-by: Ming Lei <ming.lei@canonical.com>
> ---
>  drivers/base/Kconfig          |   12 +++++++
>  drivers/base/firmware_class.c |   76 ++++++++++++++++++++++++++++++++++++-----
>  2 files changed, 80 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig
> index 07abd9d..5b0c909 100644
> --- a/drivers/base/Kconfig
> +++ b/drivers/base/Kconfig
> @@ -156,6 +156,18 @@ config FW_LOADER_USER_HELPER
>  	  no longer required unless you have a special firmware file that
>  	  resides in a non-standard path.
>  
> +config FW_CUSTOMIZED_PATH
> +	string "default firmware search paths for direct loading"
> +	help
> +	  On some distribution(e.g. android), firmware images aren't
> +	  put under kernel built-in search paths, so provide this option
> +	  for distributions to choose a distribution specific firmware
> +	  search path. The option allows to choose more than one path,
> +	  and paths are seperated with semicolon(e.g. on android, the
> +	  option might look as "/etc/firmware;/vendor/firmware").
> +
> +	  If you are unsure about this, don't choose here.
> +
>  config DEBUG_DRIVER
>  	bool "Driver Core verbose debug messages"
>  	depends on DEBUG_KERNEL
> diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
> index c743409..50b5913 100644
> --- a/drivers/base/firmware_class.c
> +++ b/drivers/base/firmware_class.c
> @@ -267,6 +267,9 @@ static void fw_free_buf(struct firmware_buf *buf)
>  static char fw_path_para[256];
>  static const char * const fw_path[] = {
>  	fw_path_para,
> +#ifdef CONFIG_FW_CUSTOMIZED_PATH
> +	CONFIG_FW_CUSTOMIZED_PATH,
> +#endif
>  	"/lib/firmware/updates/" UTS_RELEASE,
>  	"/lib/firmware/updates",
>  	"/lib/firmware/" UTS_RELEASE,
> @@ -314,6 +317,59 @@ static bool fw_read_file_contents(struct file *file, struct firmware_buf *fw_buf
>  	return true;
>  }
>  
> +static bool fw_get_file_firmware(const char *path,
> +				 struct firmware_buf *buf)
> +{
> +	struct file *file;
> +	bool success;
> +
> +	file = filp_open(path, O_RDONLY, 0);
> +	if (IS_ERR(file))
> +		return false;
> +	success = fw_read_file_contents(file, buf);
> +	fput(file);
> +
> +	return success;
> +}
> +
> +#ifdef CONFIG_FW_CUSTOMIZED_PATH
> +/* The path in @paths is seperated by ';' */
> +static bool fw_get_fw_file_from_paths(const char *paths, char *path,
> +				      struct firmware_buf *buf)
> +{
> +	int len, start, end;
> +	char *pos;
> +
> +	end = -1;
> +	do {
> +		start = end + 1;
> +		pos = strchr(&paths[start], ';');
> +		if (pos) {
> +			end = (int)(pos - paths);
> +			len = end - start;
> +		} else {
> +			len = strlen(&paths[start]);
> +		}
> +
> +		if (PATH_MAX < len + strlen(buf->fw_id))
> +			continue;
> +		strncpy(path, &paths[start], len);
> +		snprintf(&path[len], PATH_MAX - len, "/%s", buf->fw_id);
> +
> +		if (fw_get_file_firmware(path, buf))
> +			return true;
> +	} while (pos && end < strlen(paths) - 1);
> +
> +	return false;
> +}
> +#else
> +static bool fw_get_fw_file_from_paths(const char *paths, char *path,
> +				      struct firmware_buf *buf)
> +{
> +	return false;
> +}
> +#endif
> +
>  static bool fw_get_filesystem_firmware(struct device *device,
>  				       struct firmware_buf *buf)
>  {
> @@ -322,19 +378,23 @@ static bool fw_get_filesystem_firmware(struct device *device,
>  	char *path = __getname();
>  
>  	for (i = 0; i < ARRAY_SIZE(fw_path); i++) {
> -		struct file *file;
>  
>  		/* skip the unset customized path */
>  		if (!fw_path[i][0])
>  			continue;
>  
> -		snprintf(path, PATH_MAX, "%s/%s", fw_path[i], buf->fw_id);
> -
> -		file = filp_open(path, O_RDONLY, 0);
> -		if (IS_ERR(file))
> -			continue;
> -		success = fw_read_file_contents(file, buf);
> -		fput(file);
> +		/*
> +		 * If CONFIG_FW_CUSTOMIZED_PATH is set, search from
> +		 * these paths first
> +		 */
> +		if (i == 1 && ARRAY_SIZE(fw_path) > 5) {
> +			success = fw_get_fw_file_from_paths(fw_path[1],
> +							    path, buf);
> +		} else {
> +			snprintf(path, PATH_MAX, "%s/%s", fw_path[i],
> +				 buf->fw_id);
> +			success = fw_get_file_firmware(path, buf);

Shouldn't fw_get_fw_file_from_paths() be applied unconditionally?
It'll be benefit for the customized path passed via module option,
too.  The only drawback is a slight code growth, but the code can be
reduced a bit with strcspn() or such.

BTW, I now wonder what happens if you pass a relative path.
Did you already test it?


thanks,

Takashi