Re: [PATCH v3 08/13] hw/arm/raspi: Make board_rev a field of RaspiMachineClass

From: Igor Mammedov <imammedo@redhat.com>
To: "Philippe Mathieu-Daudé" <philmd@redhat.com>
Cc: "Peter Maydell" <peter.maydell@linaro.org>,
	"Joaquin de Andres" <me@xcancerberox.com.ar>,
	"Alistair Francis" <alistair@alistair23.me>,
	"Philippe Mathieu-Daudé" <f4bug@amsat.org>,
	"Andrew Baumann" <Andrew.Baumann@microsoft.com>,
	qemu-devel@nongnu.org, "Esteban Bosse" <estebanbosse@gmail.com>,
	"Niek Linnenbank" <nieklinnenbank@gmail.com>,
	qemu-arm@nongnu.org
Subject: Re: [PATCH v3 08/13] hw/arm/raspi: Make board_rev a field of RaspiMachineClass
Date: Mon, 10 Feb 2020 14:09:18 +0100	[thread overview]
Message-ID: <20200210140918.270c8a5d@redhat.com> (raw)
In-Reply-To: <2adc51a2-b526-7f6a-4c01-775f3ac06444@redhat.com>

On Mon, 10 Feb 2020 11:03:40 +0100
Philippe Mathieu-Daudé <philmd@redhat.com> wrote:

> On 2/10/20 10:50 AM, Igor Mammedov wrote:
> > On Sat,  8 Feb 2020 17:56:40 +0100
> > Philippe Mathieu-Daudé <f4bug@amsat.org> wrote:
> >   
> >> We want to have a common class_init(). The only value that
> >> matters (and changes) is the board revision.
> >> Pass the board_rev as class_data to class_init().
> >>
> >> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> >> ---
> >>   hw/arm/raspi.c | 17 ++++++++++++++---
> >>   1 file changed, 14 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/hw/arm/raspi.c b/hw/arm/raspi.c
> >> index 62b8df3c2e..fbfcd29732 100644
> >> --- a/hw/arm/raspi.c
> >> +++ b/hw/arm/raspi.c
> >> @@ -46,6 +46,7 @@ typedef struct RaspiMachineClass {
> >>       /*< private >*/
> >>       MachineClass parent_obj;
> >>       /*< public >*/
> >> +    uint32_t board_rev;
> >>   } RaspiMachineClass;
> >>   
> >>   #define TYPE_RASPI_MACHINE       MACHINE_TYPE_NAME("raspi-common")
> >> @@ -227,9 +228,11 @@ static void setup_boot(MachineState *machine, int version, size_t ram_size)
> >>       arm_load_kernel(ARM_CPU(first_cpu), machine, &binfo);
> >>   }
> >>   
> >> -static void raspi_init(MachineState *machine, uint32_t board_rev)
> >> +static void raspi_init(MachineState *machine)
> >>   {
> >> +    RaspiMachineClass *mc = RASPI_MACHINE_GET_CLASS(machine);
> >>       RaspiMachineState *s = RASPI_MACHINE(machine);
> >> +    uint32_t board_rev = mc->board_rev;
> >>       int version = board_version(board_rev);
> >>       uint64_t ram_size = board_ram_size(board_rev);
> >>       uint32_t vcram_size;
> >> @@ -279,13 +282,16 @@ static void raspi_init(MachineState *machine, uint32_t board_rev)
> >>   
> >>   static void raspi2_init(MachineState *machine)
> >>   {
> >> -    raspi_init(machine, 0xa21041);
> >> +    raspi_init(machine);
> >>   }
> >>   
> >>   static void raspi2_machine_class_init(ObjectClass *oc, void *data)
> >>   {
> >>       MachineClass *mc = MACHINE_CLASS(oc);
> >> +    RaspiMachineClass *rmc = RASPI_MACHINE_CLASS(oc);
> >> +    uint32_t board_rev = (uint32_t)(uintptr_t)data;
> >>   
> >> +    rmc->board_rev = board_rev;  
> > 
> > instead of doing a bit obscure ".class_data     = (void *)0xa21041," and
> > using it here, I'd just do
> > 
> >         rmc->board_rev = 0xa21041;
> > 
> > using value specific for each leaf class  
> 
> Leaf classes are removed in patch #12 "Use a unique 
> raspi_machine_class_init() method", see more uses of .class_data from v2:
> https://www.mail-archive.com/qemu-devel@nongnu.org/msg677164.html
> https://www.mail-archive.com/qemu-devel@nongnu.org/msg677166.html
> 
> Are you disagreeing with them? Then we should document .class_data as 
> deprecated and show example of good code.

we sometimes use .class_data when creating many derived types
(typical example CPU types (x86) ) where it's impractical to code
leaf class_init functions. I'd use .class_data in cases where I
can't get away with explicit .class_init

However in case of machines (even various versioned ones) practice
was to use parent class_init to set common data and leaf class_inits
to set board (version) specific features.

> > with this change
> >   Reviewed-by: Igor Mammedov <imammedo@redhat.com>
> >   
> >>       mc->desc = "Raspberry Pi 2B";
> >>       mc->init = raspi2_init;
> >>       mc->block_default_type = IF_SD;
> >> @@ -302,13 +308,16 @@ static void raspi2_machine_class_init(ObjectClass *oc, void *data)
> >>   #ifdef TARGET_AARCH64
> >>   static void raspi3_init(MachineState *machine)
> >>   {
> >> -    raspi_init(machine, 0xa02082);
> >> +    raspi_init(machine);
> >>   }
> >>   
> >>   static void raspi3_machine_class_init(ObjectClass *oc, void *data)
> >>   {
> >>       MachineClass *mc = MACHINE_CLASS(oc);
> >> +    RaspiMachineClass *rmc = RASPI_MACHINE_CLASS(oc);
> >> +    uint32_t board_rev = (uint32_t)(uintptr_t)data;
> >>   
> >> +    rmc->board_rev = board_rev;
> >>       mc->desc = "Raspberry Pi 3B";
> >>       mc->init = raspi3_init;
> >>       mc->block_default_type = IF_SD;
> >> @@ -327,11 +336,13 @@ static const TypeInfo raspi_machine_types[] = {
> >>           .name           = MACHINE_TYPE_NAME("raspi2"),
> >>           .parent         = TYPE_RASPI_MACHINE,
> >>           .class_init     = raspi2_machine_class_init,
> >> +        .class_data     = (void *)0xa21041,
> >>   #ifdef TARGET_AARCH64
> >>       }, {
> >>           .name           = MACHINE_TYPE_NAME("raspi3"),
> >>           .parent         = TYPE_RASPI_MACHINE,
> >>           .class_init     = raspi3_machine_class_init,
> >> +        .class_data     = (void *)0xa02082,
> >>   #endif
> >>       }, {
> >>           .name           = TYPE_RASPI_MACHINE,  
> >   
> 