Re: [PATCH] Semihost SYS_READC implementation (v4)

["Keith Packard" <keithp@keithp.com>]

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Peter Maydell <peter.maydell@linaro.org> writes:

> I'm going to push for somebody actually writing out a
> document and putting it somewhere that we can point to
> and say "that's the authoritative spec", please...
> it doesn't have to be a big formal thing, but I do
> think you want it written down, because the whole point
> is for multiple implementations and users to interoperate.

I can work within the RISC-V foundation to get an 'official' document
written. Having a handful of existing inter-operable implementations
will make that really easy to do :-)

> Yeah, the mux works fine for this kind of thing. There's
> no inherent reason why semihosting ought to "win" as
> the initially selected thing on the mux, though --
> typically that would be expected to be the UART/serial
> console.

That would just require moving the call to qemu_semihosting_console_init
up in the function. Doesn't really matter to me; I suspect that most
users will either user serial or semihosting, but probably not both
(except when debugging the serial driver).

This does the trick (on top of the latest patch). Let me know if this is
what you want. To get semihosting to be first, you have to disable the
serial driver if the hardware has a serial port:

        qemu -chardev stdio,mux=on,id=stdio0 \
             -serial null \
             -semihosting-config enable=on,chardev=stdio0 \
             -mon chardev=stdio0,mode=readline"

diff --git a/vl.c b/vl.c
index ac584d97ea..7ea8a907fd 100644
--- a/vl.c
+++ b/vl.c
@@ -4284,6 +4284,9 @@ int main(int argc, char **argv, char **envp)
     qemu_opts_foreach(qemu_find_opts("mon"),
                       mon_init_func, NULL, &error_fatal);
 
+    /* connect semihosting console input if requested */
+    qemu_semihosting_console_init();
+
     if (foreach_device_config(DEV_SERIAL, serial_parse) < 0)
         exit(1);
     if (foreach_device_config(DEV_PARALLEL, parallel_parse) < 0)
@@ -4381,9 +4384,6 @@ int main(int argc, char **argv, char **envp)
     ds = init_displaystate();
     qemu_display_init(ds, &dpy);
 
-    /* connect semihosting console input if requested */
-    qemu_semihosting_console_init();
-
     /* must be after terminal init, SDL library changes signal handlers */
     os_setup_signal_handling();
 
-- 
-keith

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