And a property and rename "it_shift" field to "regshift", as it seems
to be more popular (and I don't know what "it" stands for).

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 hw/char/serial.c         | 23 ++++++++++++++++++-----
 include/hw/char/serial.h |  4 ++--
 2 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/hw/char/serial.c b/hw/char/serial.c
index 0290b3c633..c28cfc94fd 100644
--- a/hw/char/serial.c
+++ b/hw/char/serial.c
@@ -1033,7 +1033,7 @@ static uint64_t serial_mm_read(void *opaque, hwaddr addr,
                                unsigned size)
 {
     SerialMM *s = SERIAL_MM(opaque);
-    return serial_ioport_read(&s->serial, addr >> s->it_shift, 1);
+    return serial_ioport_read(&s->serial, addr >> s->regshift, 1);
 }
 
 static void serial_mm_write(void *opaque, hwaddr addr,
@@ -1041,7 +1041,7 @@ static void serial_mm_write(void *opaque, hwaddr addr,
 {
     SerialMM *s = SERIAL_MM(opaque);
     value &= 255;
-    serial_ioport_write(&s->serial, addr >> s->it_shift, value, 1);
+    serial_ioport_write(&s->serial, addr >> s->regshift, value, 1);
 }
 
 static const MemoryRegionOps serial_mm_ops[3] = {
@@ -1069,14 +1069,14 @@ static const MemoryRegionOps serial_mm_ops[3] = {
 };
 
 SerialMM *serial_mm_init(MemoryRegion *address_space,
-                            hwaddr base, int it_shift,
+                            hwaddr base, int regshift,
                             qemu_irq irq, int baudbase,
                             Chardev *chr, enum device_endian end)
 {
     SerialMM *self = SERIAL_MM(qdev_create(NULL, TYPE_SERIAL_MM));
     SerialState *s = &self->serial;
 
-    self->it_shift = it_shift;
+    qdev_prop_set_uint8(DEVICE(self), "regshift", regshift);
     s->irq = irq;
     qdev_prop_set_uint32(DEVICE(s), "baudbase", baudbase);
     qdev_prop_set_chr(DEVICE(s), "chardev", chr);
@@ -1086,7 +1086,7 @@ SerialMM *serial_mm_init(MemoryRegion *address_space,
     qdev_init_nofail(DEVICE(self));
 
     memory_region_init_io(&s->io, NULL, &serial_mm_ops[end], self,
-                          "serial", 8 << it_shift);
+                          "serial", 8 << regshift);
     memory_region_add_subregion(address_space, base, &s->io);
 
     return self;
@@ -1100,11 +1100,24 @@ static void serial_mm_instance_init(Object *o)
                             TYPE_SERIAL, &error_abort, NULL);
 }
 
+static Property serial_mm_properties[] = {
+    DEFINE_PROP_UINT8("regshift", SerialMM, regshift, 0),
+    DEFINE_PROP_END_OF_LIST(),
+};
+
+static void serial_mm_class_init(ObjectClass *klass, void* data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+
+    dc->props = serial_mm_properties;
+}
+
 static const TypeInfo serial_mm_info = {
     .name = TYPE_SERIAL_MM,
     .parent = TYPE_SYS_BUS_DEVICE,
     .instance_init = serial_mm_instance_init,
     .instance_size = sizeof(SerialMM),
+    .class_init = serial_mm_class_init,
 };
 
 static void serial_register_types(void)
diff --git a/include/hw/char/serial.h b/include/hw/char/serial.h
index f146d426c2..759c85976d 100644
--- a/include/hw/char/serial.h
+++ b/include/hw/char/serial.h
@@ -85,7 +85,7 @@ typedef struct SerialMM {
 
     SerialState serial;
 
-    int it_shift;
+    uint8_t regshift;
 } SerialMM;
 
 extern const VMStateDescription vmstate_serial;
@@ -102,7 +102,7 @@ void serial_set_frequency(SerialState *s, uint32_t frequency);
 SerialState *serial_init(int base, qemu_irq irq, int baudbase,
                          Chardev *chr, MemoryRegion *system_io);
 SerialMM *serial_mm_init(MemoryRegion *address_space,
-                         hwaddr base, int it_shift,
+                         hwaddr base, int regshift,
                          qemu_irq irq, int baudbase,
                          Chardev *chr, enum device_endian end);
 
-- 
2.23.0.606.g08da6496b6

On Wed, 23 Oct 2019 at 18:34, Marc-André Lureau
<marcandre.lureau@redhat.com> wrote:
>
> And a property and rename "it_shift" field to "regshift", as it seems
> to be more popular (and I don't know what "it" stands for).
>
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>

I have no idea what it_shift means either (I had a look in the
git history but it seems to have been added with that name
very early on when the commit logs were generally not very
informative); 'regshift' sounds good to me too.

> +static Property serial_mm_properties[] = {
> +    DEFINE_PROP_UINT8("regshift", SerialMM, regshift, 0),

This could use a comment describing what the property does.

> +    DEFINE_PROP_END_OF_LIST(),

Otherwise
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

thanks
-- PMM

Hi

On Mon, Nov 18, 2019 at 6:54 PM Peter Maydell <peter.maydell@linaro.org> wrote:
>
> On Wed, 23 Oct 2019 at 18:34, Marc-André Lureau
> <marcandre.lureau@redhat.com> wrote:
> >
> > And a property and rename "it_shift" field to "regshift", as it seems
> > to be more popular (and I don't know what "it" stands for).
> >
> > Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
>
> I have no idea what it_shift means either (I had a look in the
> git history but it seems to have been added with that name
> very early on when the commit logs were generally not very
> informative); 'regshift' sounds good to me too.
>
> > +static Property serial_mm_properties[] = {
> > +    DEFINE_PROP_UINT8("regshift", SerialMM, regshift, 0),
>
> This could use a comment describing what the property does.

"Set the register shift value"? Half-kidding, do you have better
comment to make? Otherwise, it's probably not worth.

From what I understand, it's just applying a shift on the IO addr,
probably for alignment/access arch-specific reasons. You probably know
better than me ;)

>
> > +    DEFINE_PROP_END_OF_LIST(),
>
> Otherwise
> Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
>

thanks

On Wed, 20 Nov 2019 at 07:54, Marc-André Lureau
<marcandre.lureau@redhat.com> wrote:
>
> Hi
>
> On Mon, Nov 18, 2019 at 6:54 PM Peter Maydell <peter.maydell@linaro.org> wrote:
> >
> > On Wed, 23 Oct 2019 at 18:34, Marc-André Lureau
> > <marcandre.lureau@redhat.com> wrote:
> > > +static Property serial_mm_properties[] = {
> > > +    DEFINE_PROP_UINT8("regshift", SerialMM, regshift, 0),
> >
> > This could use a comment describing what the property does.
>
> "Set the register shift value"? Half-kidding, do you have better
> comment to make? Otherwise, it's probably not worth.
>
> From what I understand, it's just applying a shift on the IO addr,
> probably for alignment/access arch-specific reasons. You probably know
> better than me ;)

What this is doing is defining the spacing between adjacent
registers. Some MMIO-based 16550 implementations have the registers
at byte offsets from each other (that's regshift 0). Some have
them at halfword offsets (regshift 1); and some use 4-byte
offsets (regshift 2). Something like this will do:

 /*
  * Set the spacing between adjacent memory-mapped UART registers.
  * Each register will be at (1 << regshift) bytes after the previous one.
  */

(basically the comment bridges the gap between what I know as
somebody trying to use the 16550 model, ie the behaviour of
the hardware I'm trying to model, and what I need to do to configure
the QEMU code to give that behaviour.)

thanks
-- PMM