On Mon, 21 Dec 2015, Jani Nikula <jani.nikula@xxxxxxxxx> wrote:
> Add an overview and documentation for the VBT/BDB header structures.
>
> Signed-off-by: Jani Nikula <jani.nikula@xxxxxxxxx>
Pushed this one patch to drm-intel-next-queued with Daniel's irc
ack. Fixed a small grammatical error while at it (*a* BDB Header).
BR,
Jani.
> ---
> Documentation/DocBook/gpu.tmpl | 6 ++++++
> drivers/gpu/drm/i915/intel_bios.c | 24 +++++++++++++++++++++++-
> drivers/gpu/drm/i915/intel_bios.h | 38 ++++++++++++++++++++++++++++----------
> 3 files changed, 57 insertions(+), 11 deletions(-)
>
> diff --git a/Documentation/DocBook/gpu.tmpl b/Documentation/DocBook/gpu.tmpl
> index 6c6e81a9eaf4..f96a5d467f84 100644
> --- a/Documentation/DocBook/gpu.tmpl
> +++ b/Documentation/DocBook/gpu.tmpl
> @@ -3507,6 +3507,12 @@ int num_ioctls;</synopsis>
> !Pdrivers/gpu/drm/i915/intel_csr.c csr support for dmc
> !Idrivers/gpu/drm/i915/intel_csr.c
> </sect2>
> + <sect2>
> + <title>Video BIOS Table (VBT)</title>
> +!Pdrivers/gpu/drm/i915/intel_bios.c Video BIOS Table (VBT)
> +!Idrivers/gpu/drm/i915/intel_bios.c
> +!Idrivers/gpu/drm/i915/intel_bios.h
> + </sect2>
> </sect1>
>
> <sect1>
> diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
> index eba3e0f87181..d487f602a10e 100644
> --- a/drivers/gpu/drm/i915/intel_bios.c
> +++ b/drivers/gpu/drm/i915/intel_bios.c
> @@ -31,6 +31,28 @@
> #include "i915_drv.h"
> #include "intel_bios.h"
>
> +/**
> + * DOC: Video BIOS Table (VBT)
> + *
> + * The Video BIOS Table, or VBT, provides platform and board specific
> + * configuration information to the driver that is not discoverable or available
> + * through other means. The configuration is mostly related to display
> + * hardware. The VBT is available via the ACPI OpRegion or, on older systems, in
> + * the PCI ROM.
> + *
> + * The VBT consists of a VBT Header (defined as &struct vbt_header), BDB Header
> + * (&struct bdb_header), and a number of BIOS Data Blocks (BDB) that contain the
> + * actual configuration information. The VBT Header, and thus the VBT, begins
> + * with "$VBT" signature. The VBT Header contains the offset of the BDB
> + * Header. The data blocks are concatenated after the BDB Header. The data
> + * blocks have a 1-byte Block ID, 2-byte Block Size, and Block Size bytes of
> + * data. (Block 53, the MIPI Sequence Block is an exception.)
> + *
> + * The driver parses the VBT during load. The relevant information is stored in
> + * driver private data for ease of use, and the actual VBT is not read after
> + * that.
> + */
> +
> #define SLAVE_ADDR1 0x70
> #define SLAVE_ADDR2 0x72
>
> @@ -1285,7 +1307,7 @@ static const struct vbt_header *find_vbt(void __iomem *bios, size_t size)
>
> /**
> * intel_bios_init - find VBT and initialize settings from the BIOS
> - * @dev: DRM device
> + * @dev_priv: i915 device instance
> *
> * Loads the Video BIOS and checks that the VBT exists. Sets scratch registers
> * to appropriate values.
> diff --git a/drivers/gpu/drm/i915/intel_bios.h b/drivers/gpu/drm/i915/intel_bios.h
> index 54eac1003a1e..2dc46a98c332 100644
> --- a/drivers/gpu/drm/i915/intel_bios.h
> +++ b/drivers/gpu/drm/i915/intel_bios.h
> @@ -28,22 +28,40 @@
> #ifndef _I830_BIOS_H_
> #define _I830_BIOS_H_
>
> +/**
> + * struct vbt_header - VBT Header structure
> + * @signature: VBT signature, always starts with "$VBT"
> + * @version: Version of this structure
> + * @header_size: Size of this structure
> + * @vbt_size: Size of VBT (VBT Header, BDB Header and data blocks)
> + * @vbt_checksum: Checksum
> + * @reserved0: Reserved
> + * @bdb_offset: Offset of &struct bdb_header from beginning of VBT
> + * @aim_offset: Offsets of add-in data blocks from beginning of VBT
> + */
> struct vbt_header {
> - u8 signature[20]; /**< Always starts with 'VBT$' */
> - u16 version; /**< decimal */
> - u16 header_size; /**< in bytes */
> - u16 vbt_size; /**< in bytes */
> + u8 signature[20];
> + u16 version;
> + u16 header_size;
> + u16 vbt_size;
> u8 vbt_checksum;
> u8 reserved0;
> - u32 bdb_offset; /**< from beginning of VBT */
> - u32 aim_offset[4]; /**< from beginning of VBT */
> + u32 bdb_offset;
> + u32 aim_offset[4];
> } __packed;
>
> +/**
> + * struct bdb_header - BDB Header structure
> + * @signature: BDB signature "BIOS_DATA_BLOCK"
> + * @version: Version of the data block definitions
> + * @header_size: Size of this structure
> + * @bdb_size: Size of BDB (BDB Header and data blocks)
> + */
> struct bdb_header {
> - u8 signature[16]; /**< Always 'BIOS_DATA_BLOCK' */
> - u16 version; /**< decimal */
> - u16 header_size; /**< in bytes */
> - u16 bdb_size; /**< in bytes */
> + u8 signature[16];
> + u16 version;
> + u16 header_size;
> + u16 bdb_size;
> } __packed;
>
> /* strictly speaking, this is a "skip" block, but it has interesting info */
--
Jani Nikula, Intel Open Source Technology Center
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