Messages in this thread | | | Subject | Re: [PATCH V1 RESEND 1/3] perf/imx_ddr: Add system PMU identifier for userspace | From | John Garry <> | Date | Thu, 21 May 2020 15:00:13 +0100 |
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On 21/05/2020 14:04, Will Deacon wrote: > On Wed, May 20, 2020 at 09:23:41AM -0600, Rob Herring wrote: >> On Wed, May 20, 2020 at 1:33 AM Will Deacon <will@kernel.org> wrote: >>> >>> On Tue, May 19, 2020 at 12:51:25PM -0600, Rob Herring wrote: >>>> On Tue, May 12, 2020 at 03:31:13PM +0800, Joakim Zhang wrote: >>>>> +static ssize_t ddr_perf_identifier_show(struct device *dev, >>>>> + struct device_attribute *attr, >>>>> + char *page) >>>>> +{ >>>>> + struct ddr_pmu *pmu = dev_get_drvdata(dev); >>>>> + >>>>> + return sprintf(page, "%s\n", pmu->devtype_data->identifier); >>>> >>>> Why do we need yet another way to identify the SoC from userspace? >>> >>> I also really dislike this. What's the preferred way to identify the SoC >>> from userspace? >> >> /proc/cpuinfo? ;) > > The *SoC*! > >> For an non-firmware specific case, I'd say soc_device should be. I'd >> guess ACPI systems don't use it and for them it's dmidecode typically. >> The other problem I have with soc_device is it is optional. >
Hi Will,
> John -- what do you think about using soc_device to expose this information, > with ACPI systems using DMI data instead?
Generally I don't think that DMI is reliable, and I saw this as the least preferred choice. I'm looking at the sysfs DMI info for my dev board, and I don't even see anything like a SoC identifier.
As for the event_source device sysfs identifier file, it would not always contain effectively the same as the SoC ID.
Certain PMUs which I'm interested in plan to have probe-able identification info available in future.
Thanks, John
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