[linux] Add a generic function for reading files from sysfs

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/include/ipxe/errfile.h

@@ -388,6 +388,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #define ERRFILE_efi_autoboot	      ( ERRFILE_OTHER | 0x00530000 )
 #define ERRFILE_efi_autoexec	      ( ERRFILE_OTHER | 0x00540000 )
 #define ERRFILE_efi_cachedhcp	      ( ERRFILE_OTHER | 0x00550000 )
+#define ERRFILE_linux_sysfs	      ( ERRFILE_OTHER | 0x00560000 )
 
 /** @} */
 

src/include/ipxe/linux_api.h

@@ -46,6 +46,7 @@ FILE_LICENCE ( GPL2_OR_LATER );
 #include <linux/ioctl.h>
 #include <linux/poll.h>
 #include <linux/fs.h>
+#include <linux/stat.h>
 #define MAP_FAILED ( ( void * ) -1 )
 #endif
 
@@ -65,6 +66,8 @@ extern ssize_t __asmcall linux_read ( int fd, void *buf, size_t count );
 extern ssize_t __asmcall linux_write ( int fd, const void *buf, size_t count );
 extern int __asmcall linux_fcntl ( int fd, int cmd, ... );
 extern int __asmcall linux_ioctl ( int fd, unsigned long request, ... );
+extern int __asmcall linux_statx ( int dirfd, const char *pathname, int flags,
+				   unsigned int mask, struct statx *statxbuf );
 extern int __asmcall linux_poll ( struct pollfd *fds, unsigned int nfds,
 				  int timeout );
 extern int __asmcall linux_nanosleep ( const struct timespec *req,

src/include/ipxe/linux_sysfs.h

@@ -0,0 +1,16 @@
+#ifndef _IPXE_LINUX_SYSFS_H
+#define _IPXE_LINUX_SYSFS_H
+
+/** @file
+ *
+ * Linux sysfs files
+ *
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER );
+
+#include <ipxe/uaccess.h>
+
+extern int linux_sysfs_read ( const char *filename, userptr_t *data );
+
+#endif /* _IPXE_LINUX_SYSFS_H */