Hello Rohit On 11/5/18 7:14 PM, Rohit Kumar wrote: > Hello Arnaud, > > > On 11/5/2018 4:43 PM, Arnaud Pouliquen wrote: >> Hello Rohit, >> >> On 11/2/18 1:06 PM, Rohit Kumar wrote: >>> On 11/2/2018 1:12 PM, Takashi Iwai wrote: >>>> On Thu, 01 Nov 2018 13:38:49 +0100, >>>> Rohit kumar wrote: >>>>> Remove no_pcm check to invoke pcm_new() for backend dai-links >>>>> too. This fixes crash in hdmi codec driver during hdmi_codec_startup() >>>>> while accessing chmap_info struct. chmap_info struct memory is >>>>> allocated in pcm_new() of hdmi codec driver which is not invoked >>>>> in case of DPCM when hdmi codec driver is part of backend dai-link. >>>>> >>>>> Below is the crash stack: >>>>> >>>>> [ 61.635493] Unable to handle kernel NULL pointer dereference at >>>>> virtual address 00000018 >>>>> .. >>>>> [ 61.666696] CM = 0, WnR = 1 >>>>> [ 61.669778] user pgtable: 4k pages, 39-bit VAs, pgd = >>>>> ffffffc0d6633000 >>>>> [ 61.676526] [0000000000000018] *pgd=0000000153fc8003, >>>>> *pud=0000000153fc8003, *pmd=0000000000000000 >>>>> [ 61.685793] Internal error: Oops: 96000046 [#1] PREEMPT SMP >>>>> [ 61.722955] CPU: 7 PID: 2238 Comm: aplay Not tainted 4.14.72 #21 >>>>> .. >>>>> [ 61.740269] PC is at hdmi_codec_startup+0x124/0x164 >>>>> [ 61.745308] LR is at hdmi_codec_startup+0xe4/0x164 >>>>> >>>>> Signed-off-by: Rohit kumar <rohitkr@xxxxxxxxxxxxxx> >>>> Did you check whether all drivers have no side-effect by this change? >>>> The hdmi-codec isn't the only driver that has pcm_new ops, so we have >>>> to make sure that such a fundamental change wouldn't bring any >>>> regressions. >>>> >>> Below are the drivers calling pcm_new() other than hdmi codec driver. >>> sound/soc/meson/axg-frddr.c >>> sound/soc/meson/axg-toddr.c >>> These two drivers are frontend DAI drivers and should not be impacted >>> because of this. >>> >>> Other than this, pcm_new() is called from sound/soc/stm/stm32_sai_sub.c >>> I could not get much info about this driver. However, it is just adding >>> kcontrols in pcm_new() which uses internal private structs in >>> get()/put(). >>> Olivier Moysan can too confirm on this. >> First, i'm answering for Olivier: no regression identified for the SAI >> driver, it is not a DPCM driver. >> >> Then i have a concern about the call of pcm_new for a no-PCM backend. >> Does it make sense? In DPCM concept, the backend is not linked to the >> PCM device... >> >> Instead, I would suggest that you add protection in HDMI_codec on >> chmap_info pointer. >> >> The drawback would be that the control is no more available...do you >> need it? > I don't need chmap_info, but ELD kcontrol is also defined in pcm_new() > which > we need. We should probably update the driver to make it compatible with > DPCM. Any suggestions? I would say force device to 0 if no_pcm (need probably to create the control in hdmi_of_xlate_dai_id instead of hdmi_codec_pcm_new). But keep in mind that solution has to work in case of multi HDMI codec instances, perhaps using prefix... Anyway, i'm not a DPCM expert so perhaps more elegant solutions exist. Regards Arnaud >> Regards >> Arnaud >> >>> Thanks, >>> Rohit >>>> thanks, >>>> >>>> Takashi > Thanks, > Rohit > _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
