Re: [PATCH 4/5] [SCSI] Do not use platform_bus as a parent

Pawel Moll
2014-08-01T17:25:26Z

On Sun, 2014-07-27 at 16:07 +0100, Greg Kroah-Hartman wrote:
> Ah, ok, it's a scsi core thing, not a driver core thing, that's less
> confusing now. For a "fallback" of a platform device, if you switch the
> lines around you should be fine, something like this patch perhaps:
>
> diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
> index 3cbb57a8b846..d8d3b294f5bc 100644
> --- a/drivers/scsi/hosts.c
> +++ b/drivers/scsi/hosts.c
> @@ -218,16 +218,16 @@ int scsi_add_host_with_dma(struct Scsi_Host *shost, struct device *dev,
> goto fail;
>
> if (!shost->shost_gendev.parent)
> - shost->shost_gendev.parent = dev ? dev : &platform_bus;
> - if (!dma_dev)
> - dma_dev = shost->shost_gendev.parent;
> -
> - shost->dma_dev = dma_dev;
> + shost->shost_gendev.parent = dev;
>
> error = device_add(&shost->shost_gendev);
> if (error)
> goto out;
>
> + if (!dma_dev)
> + dma_dev = shost->shost_gendev.parent;
> + shost->dma_dev = dma_dev;
> +
> pm_runtime_set_active(&shost->shost_gendev);
> pm_runtime_enable(&shost->shost_gendev);
> device_enable_async_suspend(&shost->shost_gendev);

But this will still make shost->dma_dev == NULL in the cases James
quoted:

On Fri, 2014-07-25 at 15:46 +0100, James Bottomley wrote:
> Yes, for DMA purposes, the parent cannot now be NULL; we'll get a panic
> in the DMA transfers if it is. A lot of the legacy ISA device on x86
> and I thought some ARM SOC devices don't pass in the parent device, so
> we hang them off a known parent.
>
> You can grep for it; these are the devices that will begin to panic if
> you apply this patch:
>
> arch/ia64/hp/sim/simscsi.c: error = scsi_add_host(host, NULL);
> drivers/scsi/a2091.c: error = scsi_add_host(instance, NULL);
> drivers/scsi/a3000.c: error = scsi_add_host(instance, NULL);
> drivers/scsi/aha152x.c: if( scsi_add_host(shpnt, NULL) ) {
> drivers/scsi/gdth.c: error = scsi_add_host(shp, NULL);
> drivers/scsi/gdth.c: error = scsi_add_host(shp, NULL);
> drivers/scsi/gvp11.c: error = scsi_add_host(instance, NULL);
> drivers/scsi/imm.c: err = scsi_add_host(host, NULL);
> drivers/scsi/pcmcia/fdomain_stub.c: if (scsi_add_host(host, NULL))
> drivers/scsi/pcmcia/nsp_cs.c: ret = scsi_add_host (host, NULL);
> drivers/scsi/pcmcia/qlogic_stub.c: if (scsi_add_host(shost, NULL))
> drivers/scsi/pcmcia/sym53c500_cs.c: if (scsi_add_host(host, NULL))
> drivers/scsi/ppa.c: err = scsi_add_host(host, NULL);
> drivers/scsi/qlogicfas.c: if (scsi_add_host(hreg, NULL))
> drivers/scsi/scsi_module.c: error = scsi_add_host(shost, NULL);
> drivers/scsi/sgiwd93.c: err = scsi_add_host(host, NULL);

Maybe the DMA API should be coping with NULL device? It seems to handle
it in a half of the methods and fails in the other half...

Pawel