Re: [PATCH RFC 2/2] hw: Replace drive_get_next() by drive_get()

[Markus Armbruster <armbru@redhat.com>]

Philippe Mathieu-Daudé <f4bug@amsat.org> writes:

> On 11/15/21 13:55, Markus Armbruster wrote:
>> drive_get_next() is basically a bad idea.  It returns the "next" block
>> backend of a certain interface type.  "Next" means bus=0,unit=N, where
>> subsequent calls count N up from zero, per interface type.
>> 
>> This lets you define unit numbers implicitly by execution order.  If the
>> order changes, or new calls appear "in the middle", unit numbers change.
>> ABI break.  Hard to spot in review.
>> 
>> Explicit is better than implicit: use drive_get() directly.
>> 
>> Signed-off-by: Markus Armbruster <armbru@redhat.com>
>> ---
>>  include/sysemu/blockdev.h           |  1 -
>>  blockdev.c                          | 10 ----------
>>  hw/arm/aspeed.c                     | 21 +++++++++++++--------
>>  hw/arm/cubieboard.c                 |  2 +-
>>  hw/arm/imx25_pdk.c                  |  2 +-
>>  hw/arm/integratorcp.c               |  2 +-
>>  hw/arm/mcimx6ul-evk.c               |  2 +-
>>  hw/arm/mcimx7d-sabre.c              |  2 +-
>>  hw/arm/msf2-som.c                   |  2 +-
>>  hw/arm/npcm7xx_boards.c             |  6 +++---
>>  hw/arm/orangepi.c                   |  2 +-
>>  hw/arm/raspi.c                      |  2 +-
>>  hw/arm/realview.c                   |  2 +-
>>  hw/arm/sabrelite.c                  |  2 +-
>>  hw/arm/versatilepb.c                |  4 ++--
>>  hw/arm/vexpress.c                   |  6 +++---
>>  hw/arm/xilinx_zynq.c                | 16 +++++++++-------
>>  hw/arm/xlnx-versal-virt.c           |  3 ++-
>>  hw/arm/xlnx-zcu102.c                |  6 +++---
>>  hw/microblaze/petalogix_ml605_mmu.c |  2 +-
>>  hw/misc/sifive_u_otp.c              |  2 +-
>>  hw/riscv/microchip_pfsoc.c          |  2 +-
>>  hw/sparc64/niagara.c                |  2 +-
>>  23 files changed, 49 insertions(+), 52 deletions(-)
>
>> @@ -435,11 +438,13 @@ static void aspeed_machine_init(MachineState *machine)
>>      }
>>  
>>      for (i = 0; i < bmc->soc.sdhci.num_slots; i++) {
>> -        sdhci_attach_drive(&bmc->soc.sdhci.slots[i], drive_get_next(IF_SD));
>> +        sdhci_attach_drive(&bmc->soc.sdhci.slots[i],
>> +                           drive_get(IF_SD, 0, i));
>
> If we put SD on bus #0, ...
>
>>      }
>>  
>>      if (bmc->soc.emmc.num_slots) {
>> -        sdhci_attach_drive(&bmc->soc.emmc.slots[0], drive_get_next(IF_SD));
>> +        sdhci_attach_drive(&bmc->soc.emmc.slots[0],
>> +                           drive_get(IF_SD, 0, bmc->soc.sdhci.num_slots));
>
> ... we'd want to put eMMC on bus #1

Using separate buses for different kinds of devices would be neater, but
it also would be an incompatible change.  This patch keeps existing
bus/unit numbers working.  drive_get_next() can only use bus 0.

>                                      but I see having eMMC cards on a
> IF_SD bus as a bug, since these cards are soldered on the board.

IF_SD is not a bus, it's an "block interface type", which is really just
a user interface thing.

>> --- a/hw/arm/vexpress.c
>> +++ b/hw/arm/vexpress.c
>> @@ -625,7 +625,7 @@ static void vexpress_common_init(MachineState *machine)
>>                            qdev_get_gpio_in(sysctl, ARM_SYSCTL_GPIO_MMC_WPROT));
>>      qdev_connect_gpio_out_named(dev, "card-inserted", 0,
>>                            qdev_get_gpio_in(sysctl, ARM_SYSCTL_GPIO_MMC_CARDIN));
>> -    dinfo = drive_get_next(IF_SD);
>> +    dinfo = drive_get(IF_SD, 0, 0);
>
> Can we have one interface refactor per patch (IF_SD, IF_PFLASH, IF_MTD...)?

Peter asked for one patch per "board/SoC model".  I'll do whatever helps
reviewers.

>> @@ -657,7 +657,7 @@ static void vexpress_common_init(MachineState *machine)
>>  
>>      sysbus_create_simple("pl111", map[VE_CLCD], pic[14]);
>>  
>> -    dinfo = drive_get_next(IF_PFLASH);
>> +    dinfo = drive_get(IF_PFLASH, 0, 0);
>
>> -static inline void zynq_init_spi_flashes(uint32_t base_addr, qemu_irq irq,
>> -                                         bool is_qspi)
>> +static inline int zynq_init_spi_flashes(uint32_t base_addr, qemu_irq irq,
>> +                                        bool is_qspi, int unit0)
>>  {
>> +    int unit = unit0;
>>      DeviceState *dev;
>>      SysBusDevice *busdev;
>>      SSIBus *spi;
>> @@ -156,7 +157,7 @@ static inline void zynq_init_spi_flashes(uint32_t base_addr, qemu_irq irq,
>>          spi = (SSIBus *)qdev_get_child_bus(dev, bus_name);
>>  
>>          for (j = 0; j < num_ss; ++j) {
>> -            DriveInfo *dinfo = drive_get_next(IF_MTD);
>> +            DriveInfo *dinfo = drive_get(IF_MTD, 0, unit++);
>
>> diff --git a/hw/arm/xlnx-zcu102.c b/hw/arm/xlnx-zcu102.c
>> index 3dc2b5e8ca..45eb19ab3b 100644
>> --- a/hw/arm/xlnx-zcu102.c
>> +++ b/hw/arm/xlnx-zcu102.c
>> @@ -190,7 +190,7 @@ static void xlnx_zcu102_init(MachineState *machine)
>>          BusState *spi_bus;
>>          DeviceState *flash_dev;
>>          qemu_irq cs_line;
>> -        DriveInfo *dinfo = drive_get_next(IF_MTD);
>> +        DriveInfo *dinfo = drive_get(IF_MTD, 0, i);
>
> If this is bus #0, ...
>
>>          gchar *bus_name = g_strdup_printf("spi%d", i);
>>  
>>          spi_bus = qdev_get_child_bus(DEVICE(&s->soc), bus_name);
>> @@ -212,7 +212,7 @@ static void xlnx_zcu102_init(MachineState *machine)
>>          BusState *spi_bus;
>>          DeviceState *flash_dev;
>>          qemu_irq cs_line;
>> -        DriveInfo *dinfo = drive_get_next(IF_MTD);
>> +        DriveInfo *dinfo = drive_get(IF_MTD, 0, XLNX_ZYNQMP_NUM_SPIS + i);
>
> ... I'd expect we use bus #1 here (different connector on the board).

See above.

>>          int bus = i / XLNX_ZYNQMP_NUM_QSPI_BUS_CS;
>>          gchar *bus_name = g_strdup_printf("qspi%d", bus);