Re: [PATCH v4] firmware_loader: add search= module option for multi-path firmware lookup

[Jeff Layton <jlayton@kernel.org>]

On Fri, 2026-03-20 at 16:59 +0100, Greg Kroah-Hartman wrote:
> On Fri, Mar 20, 2026 at 11:32:29AM -0400, Jeff Layton wrote:
> > Refactor fw_get_filesystem_firmware() by extracting the per-path
> > firmware loading logic into a new fw_try_firmware_path() helper.
> > 
> > Add a new firmware_class.search= module option that accepts a
> > ':'-separated list of firmware search directories. The firmware
> > lookup order is:
> > 
> >   1. firmware_class.path= (single legacy path)
> >   2. firmware_class.search= (colon-separated paths)
> >   3. Built-in default paths (/lib/firmware/updates/..., /lib/firmware)
> > 
> > A backslash can be used as an escape character, allowing a literal
> > ':' ('\:') or literal '\' ('\\') to be embedded in a pathname.
> > 
> > Example:
> > 
> >   firmware_class.search=/custom/path1:/custom/path2
> > 
> > Suggested-by: Michal Grzedzicki <mge@meta.com>
> > Signed-off-by: Jeff Layton <jlayton@kernel.org>
> > ---
> > This version adds a new module option called "search=" to specify an
> > (escapable) search path. The search= path is tried after the original
> > (unescaped) path= string, but before the hardcoded search path.
> > ---
> > Changes in v4:
> > - Move search path to new search= option that is tried after path=
> > - Link to v3: https://lore.kernel.org/r/20260318-fw-path-v3-1-a701a08bc025@kernel.org
> > 
> > Changes in v3:
> > - Allow '\' to escape a literal ':' or '\' in the string
> > - Link to v2: https://lore.kernel.org/r/20260318-fw-path-v2-1-8a106eb91eb4@kernel.org
> > 
> > Changes in v2:
> > - switch to using ':' as path delimiter
> > - Link to v1: https://lore.kernel.org/r/20260318-fw-path-v1-1-7884d9bf618f@kernel.org
> > ---
> >  drivers/base/firmware_loader/main.c | 224 ++++++++++++++++++++++++------------
> >  1 file changed, 150 insertions(+), 74 deletions(-)
> > 
> > diff --git a/drivers/base/firmware_loader/main.c b/drivers/base/firmware_loader/main.c
> > index a11b30dda23be563bd55f25474ceff2153ddd667..0f58d996d3807a1f57dc924adbe657360fdfac1e 100644
> > --- a/drivers/base/firmware_loader/main.c
> > +++ b/drivers/base/firmware_loader/main.c
> > @@ -469,8 +469,8 @@ static int fw_decompress_xz(struct device *dev, struct fw_priv *fw_priv,
> >  
> >  /* direct firmware loading support */
> >  static char fw_path_para[256];
> > +static char fw_search_para[256];
> >  static const char * const fw_path[] = {
> > -	fw_path_para,
> >  	"/lib/firmware/updates/" UTS_RELEASE,
> >  	"/lib/firmware/updates",
> >  	"/lib/firmware/" UTS_RELEASE,
> > @@ -485,6 +485,82 @@ static const char * const fw_path[] = {
> >  module_param_string(path, fw_path_para, sizeof(fw_path_para), 0644);
> >  MODULE_PARM_DESC(path, "customized firmware image search path with a higher priority than default path");
> 
> Change this to say "single directory location" or something like that?
> 
> >  
> > +module_param_string(search, fw_search_para, sizeof(fw_search_para), 0644);
> 
> "search_path"?
> 
> Or "path_search"?
> 
> Naming is hard :(
> 

Indeed. I'm fine with a different name if that's the consensus.

> > +MODULE_PARM_DESC(search, "colon-separated list of firmware search paths, tried after path= (use '\\:' for literal ':', '\\\\' for literal '\\')");
> > +
> > +static int
> > +fw_try_firmware_path(struct device *device, struct fw_priv *fw_priv,
> > +		     const char *suffix,
> > +		     int (*decompress)(struct device *dev,
> > +				       struct fw_priv *fw_priv,
> > +				       size_t in_size,
> > +				       const void *in_buffer),
> > +		     const char *dir, int dirlen,
> > +		     char *path, void **bufp, size_t msize)
> > +{
> > +	size_t file_size = 0;
> > +	size_t *file_size_ptr = NULL;
> > +	size_t size;
> > +	int len, rc;
> > +
> > +	len = snprintf(path, PATH_MAX, "%.*s/%s%s",
> > +		       dirlen, dir, fw_priv->fw_name, suffix);
> > +	if (len >= PATH_MAX)
> > +		return -ENAMETOOLONG;
> > +
> > +	fw_priv->size = 0;
> > +
> > +	/*
> > +	 * The total file size is only examined when doing a partial
> > +	 * read; the "full read" case needs to fail if the whole
> > +	 * firmware was not completely loaded.
> > +	 */
> > +	if ((fw_priv->opt_flags & FW_OPT_PARTIAL) && *bufp)
> > +		file_size_ptr = &file_size;
> > +
> > +	/* load firmware files from the mount namespace of init */
> > +	rc = kernel_read_file_from_path_initns(path, fw_priv->offset,
> > +					       bufp, msize,
> > +					       file_size_ptr,
> > +					       READING_FIRMWARE);
> > +	if (rc < 0) {
> > +		if (!(fw_priv->opt_flags & FW_OPT_NO_WARN)) {
> > +			if (rc != -ENOENT)
> > +				dev_warn(device,
> > +					 "loading %s failed with error %d\n",
> > +					 path, rc);
> > +			else
> > +				dev_dbg(device,
> > +					"loading %s failed for no such file or directory.\n",
> > +					path);
> > +		}
> > +		return rc;
> > +	}
> > +	size = rc;
> > +
> > +	dev_dbg(device, "Loading firmware from %s\n", path);
> > +	if (decompress) {
> > +		dev_dbg(device, "f/w decompressing %s\n",
> > +			fw_priv->fw_name);
> > +		rc = decompress(device, fw_priv, size, *bufp);
> > +		/* discard the superfluous original content */
> > +		vfree(*bufp);
> > +		*bufp = NULL;
> > +		if (rc) {
> > +			fw_free_paged_buf(fw_priv);
> > +			return rc;
> > +		}
> > +	} else {
> > +		dev_dbg(device, "direct-loading %s\n",
> > +			fw_priv->fw_name);
> > +		if (!fw_priv->data)
> > +			fw_priv->data = *bufp;
> > +		fw_priv->size = size;
> > +	}
> > +	fw_state_done(fw_priv);
> > +	return 0;
> > +}
> > +
> >  static int
> >  fw_get_filesystem_firmware(struct device *device, struct fw_priv *fw_priv,
> >  			   const char *suffix,
> > @@ -493,10 +569,9 @@ fw_get_filesystem_firmware(struct device *device, struct fw_priv *fw_priv,
> >  					     size_t in_size,
> >  					     const void *in_buffer))
> >  {
> > -	size_t size;
> > -	int i, len, maxlen = 0;
> > +	int i;
> >  	int rc = -ENOENT;
> > -	char *path, *nt = NULL;
> > +	char *path;
> >  	size_t msize = INT_MAX;
> >  	void *buffer = NULL;
> >  
> > @@ -511,83 +586,84 @@ fw_get_filesystem_firmware(struct device *device, struct fw_priv *fw_priv,
> >  		return -ENOMEM;
> >  
> >  	wait_for_initramfs();
> > -	for (i = 0; i < ARRAY_SIZE(fw_path); i++) {
> > -		size_t file_size = 0;
> > -		size_t *file_size_ptr = NULL;
> > -
> > -		/* skip the unset customized path */
> > -		if (!fw_path[i][0])
> > -			continue;
> > -
> > -		/* strip off \n from customized path */
> > -		maxlen = strlen(fw_path[i]);
> > -		if (i == 0) {
> > -			nt = strchr(fw_path[i], '\n');
> > -			if (nt)
> > -				maxlen = nt - fw_path[i];
> > -		}
> >  
> > -		len = snprintf(path, PATH_MAX, "%.*s/%s%s",
> > -			       maxlen, fw_path[i],
> > -			       fw_priv->fw_name, suffix);
> > -		if (len >= PATH_MAX) {
> > -			rc = -ENAMETOOLONG;
> > -			break;
> > -		}
> > +	/* Try the single customized path first */
> > +	if (fw_path_para[0]) {
> > +		int dirlen = strlen(fw_path_para);
> >  
> > -		fw_priv->size = 0;
> > +		/* strip trailing newline */
> > +		if (fw_path_para[dirlen - 1] == '\n')
> > +			dirlen--;
> 
> Why don't we just do all the "parsing" and stripping at startup (and
> when a new option is written), so we don't have to do it each and every
> time we search for a firmware image?  That would put all of the
> "cleanup" logic in one place and reduce the churn a bit.
> 
> Yes, it would require another local variable, but that should be fine.
> 

Ok, I'll see what I can do.

Thanks,
-- 
Jeff Layton <jlayton@kernel.org>