Re: [RFC PATCH 1/2] ACPI / PNP: Don't add "enumeration_by_parent" devices

[John Garry]

On 26/04/2018 15:23, John Garry wrote:

+

> On 26/04/2018 15:08, Mika Westerberg wrote:
> > On Thu, Apr 26, 2018 at 02:49:49PM +0100, John Garry wrote:
> > > diff --git a/drivers/bus/hisi_lpc.c b/drivers/bus/hisi_lpc.c
> > > index 2d4611e..b04425b 100644
> > > --- a/drivers/bus/hisi_lpc.c
> > > +++ b/drivers/bus/hisi_lpc.c
> > > @@ -18,6 +18,8 @@
> > >  #include <linux/of_platform.h>
> > >  #include <linux/pci.h>
> > >  #include <linux/slab.h>
> > > +#include <linux/serial_8250.h>
> > > +#include "../tty/serial/8250/8250.h"
> > >
> > >  #define DRV_NAME "hisi-lpc"
> > >
> > > @@ -345,6 +347,7 @@ static void hisi_lpc_comm_outs(void *hostdata,
> > > unsigned
> > > long pio,
> > >  #define MFD_CHILD_NAME_LEN (ACPI_ID_LEN +
> > > sizeof(MFD_CHILD_NAME_PREFIX) -
> > > 1)
> > >
> > >  struct hisi_lpc_mfd_cell {
> > > +    struct plat_serial8250_port serial8250_port;
> > >      struct mfd_cell_acpi_match acpi_match;
> > >      char name[MFD_CHILD_NAME_LEN];
> > >      char pnpid[ACPI_ID_LEN];
> > > @@ -513,10 +516,31 @@ static int hisi_lpc_acpi_probe(struct device
> > > *hostdev)
> > >          dev_warn(&child->dev, "set resource fail (%d)\n", ret);
> > >              return ret;
> > >          }
> > > +    if (!strcmp(acpi_device_hid(child), "HISI1031")) {
>
> Hi Mika,
>
> > Hmm, there is a way in struct mfd_cell to match child devices using _HID
> > so is there something preventing you from using that?
>
> Not that I know about. Can you describe this method? I guess I also
> don't need to set the mfd_cell pnpid either for this special case device.

So we using the mfd_cell to match child devices using _HID. At a glance, 
I don't actually see other drivers to use mfd_cell_acpi_match.pnpid .

Anyway we don't use static tables as we need to update the resources of 
the cell dynamically. However I do look at a driver like 
intel_quark_i2c_gpio.c, and this dynamically modifies the value of 
global mfd_cell array here:
https://elixir.bootlin.com/linux/latest/source/drivers/mfd/intel_quark_i2c_gpio.c#L266

I know the cell array is only used at probe time, but this did not look 
to be good standard practice to me.

Thanks,
John

> Thanks,
> John
>
>
> > .