int drm_agp_alloc (struct inode * inode, struct file * filp, unsigned int cmd, unsigned long arg);
\param inode device inode. \param filp file pointer. \param cmd command. \param arg pointer to a drm_agp_buffer structure. \return zero on success or a negative number on failure.
Verifies the AGP device is present and has been acquired, allocates the memory via alloc_agp and creates a drm_agp_mem entry for it.