Re: [PATCH v8 0/5] Enhance RPMsg buffer management

[Mathieu Poirier <mathieu.poirier@linaro.org>]

On Thu, Sep 03, 2026 at 10:28:09AM -0500, Shah, Tanmay wrote:
> 
> 
> On 9/1/2026 8:03 AM, Arnaud POULIQUEN wrote:
> > 
> > 
> > On 8/28/26 16:58, Tanmay Shah wrote:
> >> Current design uses fixed (512 bytes) rpmsg buffer size in both rx and
> >> tx directions. This design is not suitable if the payload is larger than
> >> 512 bytes or the payload is very small and doesn't need that much
> >> memory. Instead introduce new virtio feature to retrieve rpmsg tx buf
> >> size and rx buf size from the virtio config space in the resource table.
> > 
> > This version seems good to me, with or without my suggestion in patch 4/5
> > 
> > Acked-by: Arnaud Pouliquen <arnaud.pouliquen@foss.st.com>
> > 
> > Thanks!
> > 
> > Arnaud
> > 
> 
> Thank You Arnaud.
> 
> If I end up spinning another revision with any more comments, then I
> will address suggestion in the patch 4/5 as well. If I get Mathieu's RB
> for this series, then we can merge this series as it is.
> 

I edited 4/5 to include Arnaud's suggestion and applied this set.

> Tanmay
> 
> >>
> >> Changes in v8:
> >>    - fix commit message of 3/5, "%s/enable/Enabled"
> >>    - introduce new function to get buffer size for the vdev device
> >>    - fix description of VIRTIO_RPMSG_F_BUFSZ define
> >>    - "%s/or differnt RX and TX sizes)/or different RX and TX queue
> >> sizes)/"
> >>
> >> Changes in v7:
> >>    - Fix 5/5 commit text, and move change log out of commit text
> >>
> >> Changes in v6:
> >>    - remove buffer alignment from config space
> >>    - rpmsg.rst: modify alignment related documentation
> >>
> >> Changes in v5:
> >>    - fix documentation about alignment of the buffer size
> >>    - change version field from u16 to u8
> >>    - remove buffer alignment check
> >>    - Separate buffer alignment vs MTU of a single buffer
> >>    - Use buffer alignment only to get next buffer address at alignment
> >>      boundary
> >>
> >> Changes in v4:
> >>    - Introduce new patch to modify rpmsg.rst documentation
> >>    - check version is always 1.
> >>    - check size field is same as size of struct virtio_rpmsg_config
> >>    - introduce alignment field
> >>    - check alignment field is power of 2
> >>    - check tx and rx buf size is aligned with alignment passed in the
> >>      structure
> >>    - check msg size is < MTU size
> >>
> >> Changes in v3:
> >>    - new patch [1/4] that renames variables with clear names.
> >>    - %s/rbufs/rx_bufs/
> >>    - %s/sbufs/tx_bufs/
> >>    - %s/last_sbuf/last_tx_buf/
> >>    - add num_rx_buf and num_tx_buf in the documentation
> >>    - change version field from u16 to u8
> >>    - introduce size field in the rpmsg_virtio_config structure
> >>    - check version field is set to any non-zero value.
> >>    - check size field is not 0.
> >>    - Remove field for private config, as not needed for now.
> >>    - add documentation of rpmsg_virtio_config structure
> >>    - Check for error when retrieving MTU size in the sample driver
> >>    - %s/mtu/MTU/
> >>
> >> Changes in v2:
> >>    - Change author
> >>    - fix commit message with better explanation
> >>    - %s/sbuf/tx_buf
> >>    - %s/rbuf/rx_buf
> >>    - %s/num_rbuf/num_rx_buf/
> >>    - %s/num_sbuf/num_tx_buf/
> >>    - %s/sbuf_size/tx_buf_size/
> >>    - %s/rbuf_size/rx_buf_size/
> >>    - fix typo
> >>    - do not use ALIGN on buf size, rely on allocator
> >>    - make err msg more explicit, %s/vdev config:/bad vdev config/
> >>    - fix license and add AMD copyrights in the header virtio_rpmsg.h
> >>    - Assign bit 1 to VIRTIO_RPMSG_F_BUFSZ feature
> >>    - use __virtio32 over __u32
> >>    - add version field to virtio rpmsg config structure
> >>    - Introduce new patch to print rpmsg mtu size in the sample rpmsg
> >> driver
> >>    - move linux/virtio_rpmsg.h to linux/rpmsg/virtio_rpmsg.h
> >>
> >>
> >> Tanmay Shah (5):
> >>    rpmsg: virtio_rpmsg_bus: rename rbufs and sbufs
> >>    rpmsg: virtio_rpmsg_bus: allow different size of tx and rx bufs
> >>    rpmsg: virtio_rpmsg_bus: get buffer size from config space
> >>    docs: rpmsg: add virtio config space details
> >>    samples: rpmsg: add MTU size info
> >>
> >>   Documentation/staging/rpmsg.rst     |  17 +++
> >>   drivers/rpmsg/virtio_rpmsg_bus.c    | 156 +++++++++++++++++++---------
> >>   include/linux/rpmsg/virtio_rpmsg.h  |  41 ++++++++
> >>   samples/rpmsg/rpmsg_client_sample.c |  20 +++-
> >>   4 files changed, 186 insertions(+), 48 deletions(-)
> >>   create mode 100644 include/linux/rpmsg/virtio_rpmsg.h
> >>
> >>
> >> base-commit: d4d61a4b0a52e8f3cdb3e1578602850a3452ec3e
> > 
>