Thank you for the explanation. However, could you suggest, which condition should I check then? Device tree?
> -----Original Message----- > From: Sudeep Holla <sudeep.ho...@arm.com> > Sent: Thursday, May 24, 2018 17:01 > To: ilia...@codeaurora.org; vire...@kernel.org; n...@ti.com; > sb...@kernel.org; r...@kernel.org; mark.rutl...@arm.com; > r...@rjwysocki.net > Cc: Sudeep Holla <sudeep.ho...@arm.com>; linux...@vger.kernel.org; > devicet...@vger.kernel.org; linux-kernel@vger.kernel.org > Subject: Re: [PATCH v12 1/2] cpufreq: Add Kryo CPU scaling driver > > > > On 24/05/18 14:03, ilia...@codeaurora.org wrote: > > > > > > [...] > > >>> + > >>> + ret = PTR_ERR_OR_ZERO(platform_device_register_simple( > >>> + "qcom-cpufreq-kryo", -1, NULL, 0)); > >> > >> > >> You simply can't do this unconditionally here. This will blow up on > >> platforms where this driver is not supposed to work. The probe will > >> be called on non- QCOM or non-Kryo QCOM platforms and I reckon it > >> will crash trying to execute something in qcom_smem_get. > > > > What do you mean by 'unconditionally'? > > Why should you even add/register a device "qcom-cpufreq-kryo" on other > platforms. Drivers can get registered, but only devices that are present or > required by the platform need to be registered. > > > The driver depends on the smem and nvmem drivers, which depend on > ARCH_QCOM: > > + depends on QCOM_QFPROM > > + depends on QCOM_SMEM > > > > Sure, but we have something called single image for all ARM64 platforms. > May be QCOM still used to tweeking config to build binary for your particular > mobile platform but the distro kernel need single binary to work on all > platforms. We have moved far away from platform specific builds long back > now IIRC. > > > And if SMEM read in the probe returns something other than Kryo, it will > exit. > > > > Check what this driver does ? > > msm_id = qcom_smem_get(QCOM_SMEM_HOST_ANY, > MSM_ID_SMEM, &len); > msm_id++; > switch ((enum _msm_id)*msm_id) > > I think it *will and should* crash here ? You need to check the return value > for sure. But since qcom_smem_get return -EPROBE_DEFER, we keep > retrying even on non QCOM platforms which is something I would like to > avoid. > > Therefore that's not the main concern. Why do I have to see "qcom-cpufreq- > kryo" device registered on my non QCOM platform ? > > -- > Regards, > Sudeep
