bes2600: use request_firmware() for factory.txt read

The BES2600 factory calibration file (bes2600_factory.txt) was being read
via filp_open() + kernel_read() from a hard-coded absolute path baked in
at compile time via the FACTORY_PATH Makefile macro
(default: /lib/firmware/bes2600_factory.txt).

This had several problems:

1. Path mismatch - linux-firmware-style packaging (and danctnix 0.2-5
   device-pine64-pinetab2) ships the file at
   /lib/firmware/bes2600/bes2600_factory.txt, not /lib/firmware/. The
   driver logged '(NULL device *): read and check
   /lib/firmware/bes2600_factory.txt error' on every boot on PineTab2
   running linux-pinetab2 6.19.10-danctnix1-1.

2. Direct filesystem access via filp_open() / kernel_read() from a driver
   is an anti-pattern that upstream rejects: drivers should use
   request_firmware() to get binary data from userspace-managed firmware
   directories. request_firmware() natively searches the firmware_class
   path list (typically /lib/firmware + derivatives), associates the load
   with a uevent, and respects the firmware-loading infrastructure.

3. The (NULL device *) prefix in error messages indicated the absence of
   proper device-context logging. While this patch does not yet thread
   struct device through, the upstream path uses request_firmware() which
   works with dev=NULL and is the building block for a follow-up patch
   that adds per-chip device context.

Repoint the FACTORY_PATH default to the firmware-class name
(bes2600/bes2600_factory.txt) - request_firmware() prepends
/lib/firmware/ from the configured search paths. The macro remains
overridable at build time for non-standard deployments.

Rewrite factory_section_read_file() to:
  * Call request_firmware(&fw, path, NULL).
  * Size-check fw->size against FACTORY_MAX_SIZE.
  * memcpy the data into the caller's buffer.
  * Always call release_firmware() on exit.

The file write path (factory_section_write_file + kernel_write) is left
unchanged in this patch; it is the subject of a follow-up patch that
removes kernel_write and moves any remaining userspace-visible factory
configuration to a standard kernel-userspace boundary (debugfs or
nl80211 testmode).

No caller signature changes. No Makefile flag drops. Bisectable.

Tested-on: PineTab2 (BES2600WM + RK3566) running linux-pinetab2
6.19.10-danctnix1-1, deployed via /lib/modules/<ver>/extra/. Verified
post-reboot: original 'read and check /lib/firmware/bes2600_factory.txt
error' is gone; request_firmware reads the file successfully (a separate
factory_parse() bug, previously masked by the read failure, is now
exposed and tracked separately).

Signed-off-by: Markus Fritsche <fritsche.markus@gmail.com>

bes2600/Makefile

@@ -66,7 +66,7 @@ BES2600_DRV_VERSION := bes2600_0.3.5_2024.0116
 ifeq ($(CONFIG_BES2600_CALIB_FROM_LINUX),y)
 FACTORY_CRC_CHECK                    ?= n
 STANDARD_FACTORY_EFUSE_FLAG          ?= y
-FACTORY_PATH                 ?= /lib/firmware/bes2600_factory.txt
+FACTORY_PATH                 ?= bes2600/bes2600_factory.txt
 endif
 
 # basic function

bes2600/bes2600_factory.c

@@ -12,6 +12,7 @@
 #include <linux/module.h>
 #include <linux/sched.h>
 #include <linux/fs.h>
+#include <linux/firmware.h>
 #include <linux/slab.h>
 #include <linux/mutex.h>
 #include <linux/crc32.h>
@@ -137,38 +138,32 @@ static int bes2600_factory_crc_check(struct factory_t *factory_data)
  */
 static int factory_section_read_file(char *path, void *buffer)
 {
-	int ret = 0;
-	struct file *fp;
+	const struct firmware *fw;
+	int ret;
 
 	if (!path || !buffer) {
 		bes_err("%s NULL pointer err\n", __func__);
 		return -1;
 	}
 
-	bes_devel("reading %s \n", path);
+	bes_devel("requesting firmware-class %s\n", path);
 
-	fp = filp_open(path, O_RDONLY, 0); //S_IRUSR
-	if (IS_ERR(fp)) {
-		bes_devel("BES2600 : can't open %s\n",path);
+	ret = request_firmware(&fw, path, NULL);
+	if (ret) {
+		bes_devel("BES2600: request_firmware(%s) failed: %d\n", path, ret);
 		return -1;
 	}
 
-	if (fp->f_inode->i_size <= 0 || fp->f_inode->i_size > FACTORY_MAX_SIZE) {
-		bes_err(			"bes2600_factory.txt size check failed, read_size: %lld max_size: %d\n",
-			fp->f_inode->i_size, FACTORY_MAX_SIZE);
-		filp_close(fp, NULL);
+	if (fw->size == 0 || fw->size > FACTORY_MAX_SIZE) {
+		bes_err("bes2600_factory.txt size check failed, read_size: %zu max_size: %d\n",
+			fw->size, FACTORY_MAX_SIZE);
+		release_firmware(fw);
 		return -1;
 	}
 
-	ret = kernel_read(fp, buffer, fp->f_inode->i_size, &fp->f_pos);
-
-	filp_close(fp, NULL);
-
-	if (ret != fp->f_inode->i_size) {
-		bes_err("bes2600_factory.txt read fail\n");
-		ret = -1;
-	}
-
+	memcpy(buffer, fw->data, fw->size);
+	ret = (int)fw->size;
+	release_firmware(fw);
 	return ret;
 }