On Thu, Apr 25, 2019 at 07:58:28PM -0500, Jeremy Linton wrote:
> On 4/16/19 8:50 AM, Will Deacon wrote:
> > On Thu, Apr 04, 2019 at 12:24:38PM -0500, Jeremy Linton wrote:
> > > On 4/4/19 12:04 PM, Will Deacon wrote:
> > > > On Tue, Mar 26, 2019 at 05:39:38PM -0500, Jeremy Linton wrote:
> > > > > Lets add the MODULE_TABLE and platform id_table entries so that
> > > > > the SPE driver can attach to the ACPI platform device created by
> > > > > the core pmu code.
> > > > >
> > > > > Signed-off-by: Jeremy Linton <jeremy.linton@xxxxxxx>
> > > > > Reviewed-by: Sudeep Holla <sudeep.holla@xxxxxxx>
> > > > > ---
> > > > > drivers/perf/arm_spe_pmu.c | 11 +++++++++--
> > > > > 1 file changed, 9 insertions(+), 2 deletions(-)
> > > > >
> > > > > diff --git a/drivers/perf/arm_spe_pmu.c b/drivers/perf/arm_spe_pmu.c
> > > > > index 7cb766dafe85..ffa2c76c08bb 100644
> > > > > --- a/drivers/perf/arm_spe_pmu.c
> > > > > +++ b/drivers/perf/arm_spe_pmu.c
> > > > > @@ -1176,7 +1176,13 @@ static const struct of_device_id arm_spe_pmu_of_match[] = {
> > > > > };
> > > > > MODULE_DEVICE_TABLE(of, arm_spe_pmu_of_match);
> > > > > -static int arm_spe_pmu_device_dt_probe(struct platform_device *pdev)
> > > > > +static const struct platform_device_id arm_spe_match[] = {
> > > > > + { "arm,spe-v1", 0},
> > > >
> > > > It would be nice if we could avoid duplicating this string from the ACPI
> > > > parsing code.
> > >
> > > Ok sure, I just need to find a good common place for it.
>
> There doesn't appear to be a good common place for this, so maybe arm_pmu.h,
> which can then be included in the spe driver is the right thing.
I'm fine with that.
> > > > > + { }
> > > > > +};
> > > > > +MODULE_DEVICE_TABLE(platform, arm_spe_match);
> > > > > +
> > > > > +static int arm_spe_pmu_device_probe(struct platform_device *pdev)
> > > > > {
> > > > > int ret;
> > > > > struct arm_spe_pmu *spe_pmu;
> > > > > @@ -1236,11 +1242,12 @@ static int arm_spe_pmu_device_remove(struct platform_device *pdev)
> > > > > }
> > > > > static struct platform_driver arm_spe_pmu_driver = {
> > > > > + .id_table = arm_spe_match,
> > > > > .driver = {
> > > > > .name = DRVNAME,
> > > > > .of_match_table = of_match_ptr(arm_spe_pmu_of_match),
> > > >
> > > > Hmm, so some other drivers don't hook .id_table like you do, but instead
> > > > hook .acpi_match_table in the driver structure. Is that not better?
> > >
> > > This isn't actually an ACPI device, (aka not defined in the namespace), so
> > > its missing much of the ACPI functionality. I think that also means its
> > > needs to be declared this way.
> >
> > Looking at platform_match(), I'd really like to avoid having both an
> > .id_table and an .of_match_table field.
>
>
> >
> > acpi_of_match_device() will actually use the .of_match_table, but it relies
> > on ACPI_COMPANION returning a valid acpi_device. If we don't have one of
>
> Right, via the fwnode it can cause an acpi DSDT defined device with a _DSD
> "compatible" property to match an entry in the of_match_table compatible
> string. I don't think this is us...
>
> > those, perhaps we can use the .id_table exclusively and drop the
> > .of_match_table instead?
>
> This definitely made me do my homework, the following is AFAIK:
FWIW: I'm also feeling my way here!
> Its possible to match on just a .id_table, but this requires matching the OF
> device name against the id_table name rather than against the OF compatible
> string (*). This doesn't seem like a good idea, despite platform_device_id
> entries being significantly smaller than the of_device_id ones. Plus, I
> think we end up with two duplicate tables because we still need the
> MODULE_TABLE(of,xxx) to assure that userspace can associate the modalias
> with the module.
Well spotted, I didn't notice that the compatible string isn't used for
matching in that case.
> OTOH, it seems possible to match on module name directly ('arm_spe_pmu'),
> but this limits us to only a single device type for all ACPI device
> variations unless we put platform checks in the module itself (ick!). I
> suspect in the future if a spe.v2 were to come out this would be a problem
> unless a separate module were created. Then there is the fact this still
> needs a platform_device_id table, as the modalias will read
> "platform:arm_spe_pmu". Which will cause people to question why its not just
> assigned and matched against the .id_table.
Ok, fair enough and sorry for the wild goose chase. Looks like we'll stick
with what you had, as the alternatives all seen considerably worse.
Will
