Re: [PATCH v3 2/3] OvmfPkg/QemuVideoDxe: Helper functions for unaligned port I/O.

[Laszlo Ersek <lersek@redhat.com>]

On 04/05/17 11:57, Phil Dennis-Jordan wrote:
> From: Phil Dennis-Jordan <phil@philjordan.eu>
> 
> The VMWare SVGA display device implemented by Qemu (-vga vmware) uses
> an I/O-type BAR which is laid out such that some register offsets are
> not aligned to the read/write width with which they are expected to be
> accessed. (The register value port has an offset of 1 and requires
> 32 bit wide read/write access.)
> 
> The EFI_PCI_IO_PROTOCOL's Io.Read/Io.Write functions do not support
> such unaligned I/O.
> 
> Before a driver for this device can be added to QemuVideoDxe, helper
> functions for unaligned I/O are therefore required. This adds the
> functions UnalignedIoWrite32 and UnalignedIoRead32, based on IoLib's
> IoWrite32 and IoRead32, for the Ia32 and X64 architectures. Port I/O
> requires inline assembly, so implementations are provided for the GCC,
> ICC, and Microsoft compiler families. Such I/O is not possible on other
> architectures, a dummy (ASSERT()ing) implementation is therefore
> provided to satisfy the linker.
> 
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Suggested-by: Jordan Justen <jordan.l.justen@intel.com>
> Contributed-under: TianoCore Contribution Agreement 1.0
> Signed-off-by: Phil Dennis-Jordan <phil@philjordan.eu>
> Reviewed-by: Laszlo Ersek <lersek@redhat.com>
> ---
> 
> Notes:
>     v2:
>     - Separate commit for the unaligned I/O helper functions. [Laszlo]
>     - Dummy implementations return values despite ASSERT(). [Laszlo]
>     - Build failure in ArmVirtPkg fixed. [Laszlo]
>     - More consistent API docs and function ordering.
>     
>     v3:
>     - Fixed typos in commit message [Laszlo]
>     - Added Suggested-by: tag [Laszlo]
>     - Rewrapped comment lines to 79 chars [Laszlo]
>     - Corrected whitespace in function calls [Laszlo]
>     - EFIAPI dropped. [Laszlo]
>     - Fixed return value in dummy UnsignedIoWrite32 [Laszlo]
>     - Dropped "N" imm8 constraint in GCC inline asm [Laszlo]
> 
>  OvmfPkg/QemuVideoDxe/QemuVideoDxe.inf         |  6 ++
>  OvmfPkg/QemuVideoDxe/UnalignedIoInternal.h    | 59 +++++++++++++++
>  OvmfPkg/QemuVideoDxe/UnalignedIoGcc.c         | 70 +++++++++++++++++
>  OvmfPkg/QemuVideoDxe/UnalignedIoIcc.c         | 80 ++++++++++++++++++++
>  OvmfPkg/QemuVideoDxe/UnalignedIoMsc.c         | 78 +++++++++++++++++++
>  OvmfPkg/QemuVideoDxe/UnalignedIoUnsupported.c | 66 ++++++++++++++++
>  6 files changed, 359 insertions(+)

Looks good, thank you for the update.
Laszlo