[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [PATCH 4/4] serial: Allow unaligned i/o access
From: |
Michael S. Tsirkin |
Subject: |
Re: [PATCH 4/4] serial: Allow unaligned i/o access |
Date: |
Thu, 8 Sep 2022 07:15:10 -0400 |
On Thu, Sep 08, 2022 at 02:11:28PM +0400, Marc-André Lureau wrote:
> Hi
>
> On Wed, Sep 7, 2022 at 2:03 AM Arwed Meyer <arwed.meyer@gmx.de> wrote:
>
> Unaligned i/o access on serial UART works on real PCs.
> This is used for example by FreeDOS CTMouse driver. Without this it
> can't reset and detect serial mice.
>
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/77
> Signed-off-by: Arwed Meyer <arwed.meyer@gmx.de>
> ---
> hw/char/serial.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/hw/char/serial.c b/hw/char/serial.c
> index 7061aacbce..41b5e61977 100644
> --- a/hw/char/serial.c
> +++ b/hw/char/serial.c
> @@ -961,6 +961,9 @@ void serial_set_frequency(SerialState *s, uint32_t
> frequency)
> const MemoryRegionOps serial_io_ops = {
> .read = serial_ioport_read,
> .write = serial_ioport_write,
> + .valid = {
> + .unaligned = 1,
> + },
>
>
> I don't get how this can help if both min_access_size & max_access_size are 1.
>
>
> .impl = {
> .min_access_size = 1,
> .max_access_size = 1,
> --
> 2.34.1
Because that's .impl. If access is invalid we don't get as far
as breaking it up to chunks.
>
>
>
>
> --
> Marc-André Lureau