implement linux request_firmware() api in drm

[Jonathan Gray]

Tested on radeon.

This should cause no change in behaviour on inteldrm systems that require
firmware (ie skylake, kabylake, broxton) until a mountroot hook is
added and firmware installed but I have no way of testing that here.

Index: drm_linux.h
===================================================================
RCS file: /cvs/src/sys/dev/pci/drm/drm_linux.h,v
retrieving revision 1.65
diff -u -p -r1.65 drm_linux.h
--- drm_linux.h 29 Nov 2017 03:59:34 -0000      1.65
+++ drm_linux.h 12 Jan 2018 03:43:03 -0000
@@ -2161,6 +2161,7 @@ size_t sg_copy_from_buffer(struct scatte
     const void *, size_t);
 
 struct firmware {
+       size_t size;
        const u8 *data;
 };
 
@@ -2168,7 +2169,14 @@ static inline int
 request_firmware(const struct firmware **fw, const char *name,
     struct device *device)
 {
-       return -EINVAL;
+       int r;
+       struct firmware *f = malloc(sizeof(struct firmware), M_DRM, M_WAITOK);
+       *fw = f;
+       r = loadfirmware(name, __DECONST(u_char **, &f->data), &f->size);
+       if (r != 0)
+               return -r;
+       else
+               return 0;
 }
 
 #define request_firmware_nowait(a, b, c, d, e, f, g) -EINVAL
@@ -2176,6 +2184,8 @@ request_firmware(const struct firmware *
 static inline void
 release_firmware(const struct firmware *fw)
 {
+       free(__DECONST(u_char *, fw->data), M_DRM, fw->size);
+       free(__DECONST(struct firmware *, fw), M_DRM, sizeof(*fw));
 }
 
 void *memchr_inv(const void *, int, size_t);