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Re: [PATCH 4/4] serial: Allow unaligned i/o access


From: Marc-André Lureau
Subject: Re: [PATCH 4/4] serial: Allow unaligned i/o access
Date: Thu, 8 Sep 2022 14:11:28 +0400

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




--
Marc-André Lureau

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