* Allocating DMA buffer for non-PCM
@ 2013-02-14 17:03 Adrian Knoth
2013-02-14 17:14 ` Takashi Iwai
2013-02-14 17:46 ` Clemens Ladisch
0 siblings, 2 replies; 9+ messages in thread
From: Adrian Knoth @ 2013-02-14 17:03 UTC (permalink / raw)
To: alsa-devel
Hi!
Would you say that the following is the proper way to allocate a DMA
buffer used to hold level data?
struct hdspm {
struct pci_dev *pci; /* and an pci info */
struct snd_dma_buffer dmaLevelBuffer;
u32 *level_buffer; /* suitably aligned address */
[..]
}
/* allocate level buffer */
err = snd_dma_alloc_pages(SNDRV_DMA_TYPE_DEV_SG,
snd_dma_pci_data(hdspm->pci),
MADIFX_LEVEL_BUFFER_SIZE, &hdspm->dmaLevelBuffer);
if (err < 0) {
/* error */ [..]
}
hdspm->level_buffer = snd_sgbuf_get_ptr(&(hdspm->dmaLevelBuffer), 0);
memset(hdspm->level_buffer, 0, MADIFX_LEVEL_BUFFER_SIZE);
This used to work on my development machine (kernel 3.6.x), but now a
kernel 3.2.0 user reports a NULL pointer dereference of
hdspm->level_buffer, so apparently, snd_sgbuf_get_ptr() returned NULL
for him.
How could this possibly happen? Am I missing something? Better use
SNDRV_DMA_TYPE_DEV instead?
TIA
^ permalink raw reply [flat|nested] 9+ messages in thread* Re: Allocating DMA buffer for non-PCM 2013-02-14 17:03 Allocating DMA buffer for non-PCM Adrian Knoth @ 2013-02-14 17:14 ` Takashi Iwai 2013-02-14 17:26 ` Adrian Knoth 2013-02-14 17:46 ` Clemens Ladisch 1 sibling, 1 reply; 9+ messages in thread From: Takashi Iwai @ 2013-02-14 17:14 UTC (permalink / raw) To: Adrian Knoth; +Cc: alsa-devel At Thu, 14 Feb 2013 18:03:53 +0100, Adrian Knoth wrote: > > Hi! > > Would you say that the following is the proper way to allocate a DMA > buffer used to hold level data? > > struct hdspm { > struct pci_dev *pci; /* and an pci info */ > struct snd_dma_buffer dmaLevelBuffer; > u32 *level_buffer; /* suitably aligned address */ > [..] > } > > /* allocate level buffer */ > err = snd_dma_alloc_pages(SNDRV_DMA_TYPE_DEV_SG, > snd_dma_pci_data(hdspm->pci), > MADIFX_LEVEL_BUFFER_SIZE, &hdspm->dmaLevelBuffer); > if (err < 0) { > /* error */ [..] > } > > hdspm->level_buffer = snd_sgbuf_get_ptr(&(hdspm->dmaLevelBuffer), 0); hdspm->level_buffer = (u32*)hdspm.dmaLevelBuffer.area; > memset(hdspm->level_buffer, 0, MADIFX_LEVEL_BUFFER_SIZE); > > > This used to work on my development machine (kernel 3.6.x), but now a > kernel 3.2.0 user reports a NULL pointer dereference of > hdspm->level_buffer, so apparently, snd_sgbuf_get_ptr() returned NULL > for him. What's level_buffer? Is a SG-buffer for the audio stream? > How could this possibly happen? A wrong usage :) Takashi > Am I missing something? Better use > SNDRV_DMA_TYPE_DEV instead? > > > > TIA > _______________________________________________ > Alsa-devel mailing list > Alsa-devel@alsa-project.org > http://mailman.alsa-project.org/mailman/listinfo/alsa-devel > ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: Allocating DMA buffer for non-PCM 2013-02-14 17:14 ` Takashi Iwai @ 2013-02-14 17:26 ` Adrian Knoth 2013-02-15 6:22 ` Takashi Iwai 0 siblings, 1 reply; 9+ messages in thread From: Adrian Knoth @ 2013-02-14 17:26 UTC (permalink / raw) To: Takashi Iwai; +Cc: alsa-devel On 02/14/2013 06:14 PM, Takashi Iwai wrote: >> /* allocate level buffer */ >> err = snd_dma_alloc_pages(SNDRV_DMA_TYPE_DEV_SG, >> snd_dma_pci_data(hdspm->pci), >> MADIFX_LEVEL_BUFFER_SIZE, &hdspm->dmaLevelBuffer); >> if (err < 0) { >> /* error */ [..] >> } >> >> hdspm->level_buffer = snd_sgbuf_get_ptr(&(hdspm->dmaLevelBuffer), 0); > > hdspm->level_buffer = (u32*)hdspm.dmaLevelBuffer.area; Looks good, TNX. >> This used to work on my development machine (kernel 3.6.x), but now a >> kernel 3.2.0 user reports a NULL pointer dereference of >> hdspm->level_buffer, so apparently, snd_sgbuf_get_ptr() returned NULL >> for him. > What's level_buffer? The card does hardware metering and stores RMS/peak values in a DMA buffer. I want to later pass this to userspace to show signal levels, either via memcpy()ing the DMA buffer or maybe via mmap(). But since I no longer have access to such a card, work on this is on halt atm. > Is a SG-buffer for the audio stream? The audio buffers use snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_DEV_SG, snd_dma_pci_data(hdspm->pci), so they're SG, yes. >> How could this possibly happen? > A wrong usage :) I thought so, that's why I was asking. ;) Cheers and thanks again ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: Allocating DMA buffer for non-PCM 2013-02-14 17:26 ` Adrian Knoth @ 2013-02-15 6:22 ` Takashi Iwai 0 siblings, 0 replies; 9+ messages in thread From: Takashi Iwai @ 2013-02-15 6:22 UTC (permalink / raw) To: Adrian Knoth; +Cc: alsa-devel At Thu, 14 Feb 2013 18:26:53 +0100, Adrian Knoth wrote: > > On 02/14/2013 06:14 PM, Takashi Iwai wrote: > > >> /* allocate level buffer */ > >> err = snd_dma_alloc_pages(SNDRV_DMA_TYPE_DEV_SG, > >> snd_dma_pci_data(hdspm->pci), > >> MADIFX_LEVEL_BUFFER_SIZE, &hdspm->dmaLevelBuffer); > >> if (err < 0) { > >> /* error */ [..] > >> } > >> > >> hdspm->level_buffer = snd_sgbuf_get_ptr(&(hdspm->dmaLevelBuffer), 0); > > > > hdspm->level_buffer = (u32*)hdspm.dmaLevelBuffer.area; > > Looks good, TNX. > > >> This used to work on my development machine (kernel 3.6.x), but now a > >> kernel 3.2.0 user reports a NULL pointer dereference of > >> hdspm->level_buffer, so apparently, snd_sgbuf_get_ptr() returned NULL > >> for him. > > What's level_buffer? > > The card does hardware metering and stores RMS/peak values in a DMA > buffer. I want to later pass this to userspace to show signal levels, > either via memcpy()ing the DMA buffer or maybe via mmap(). But since I > no longer have access to such a card, work on this is on halt atm. > > > Is a SG-buffer for the audio stream? > > The audio buffers use > > snd_pcm_lib_preallocate_pages_for_all(pcm, > SNDRV_DMA_TYPE_DEV_SG, > snd_dma_pci_data(hdspm->pci), > > > so they're SG, yes. But isn't the level meter buffer a single page? If the buffer is only for peak meters, it can't be that big even for multi-channel cards. If so, SNDRV_DMA_TYPE_DEV_SG is utterly nonsense. Otherwise, if it's a SG buffer, you'll have to some code to set up TLB in anyway. Takashi ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: Allocating DMA buffer for non-PCM 2013-02-14 17:03 Allocating DMA buffer for non-PCM Adrian Knoth 2013-02-14 17:14 ` Takashi Iwai @ 2013-02-14 17:46 ` Clemens Ladisch 2013-02-14 17:52 ` Adrian Knoth 1 sibling, 1 reply; 9+ messages in thread From: Clemens Ladisch @ 2013-02-14 17:46 UTC (permalink / raw) To: Adrian Knoth; +Cc: alsa-devel Adrian Knoth wrote: > Would you say that the following is the proper way to allocate a DMA > buffer used to hold level data? > > err = snd_dma_alloc_pages(SNDRV_DMA_TYPE_DEV_SG, > snd_dma_pci_data(hdspm->pci), > MADIFX_LEVEL_BUFFER_SIZE, &hdspm->dmaLevelBuffer); > > hdspm->level_buffer = snd_sgbuf_get_ptr(&(hdspm->dmaLevelBuffer), 0); I don't see the code asking for the address of the second page, so I guess there isn't one. But then you don't need SG in the first place. > Better use SNDRV_DMA_TYPE_DEV instead? Yes. Regards, Clemens ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: Allocating DMA buffer for non-PCM 2013-02-14 17:46 ` Clemens Ladisch @ 2013-02-14 17:52 ` Adrian Knoth 2013-02-14 18:01 ` Clemens Ladisch 0 siblings, 1 reply; 9+ messages in thread From: Adrian Knoth @ 2013-02-14 17:52 UTC (permalink / raw) To: Clemens Ladisch; +Cc: alsa-devel On Thu, Feb 14, 2013 at 06:46:30PM +0100, Clemens Ladisch wrote: > > Would you say that the following is the proper way to allocate a DMA > > buffer used to hold level data? > > > > err = snd_dma_alloc_pages(SNDRV_DMA_TYPE_DEV_SG, > > snd_dma_pci_data(hdspm->pci), > > MADIFX_LEVEL_BUFFER_SIZE, &hdspm->dmaLevelBuffer); > > > > hdspm->level_buffer = snd_sgbuf_get_ptr(&(hdspm->dmaLevelBuffer), 0); > I don't see the code asking for the address of the second page, so I > guess there isn't one. Exactly. Just to be sure: Takashi has recommended to use (u32*)dmaLevelBuffer.area. Even in the case of SG buffers, is this virtual address continuous and safe for memset? Cheers -- mail: adi@thur.de http://adi.thur.de PGP/GPG: key via keyserver ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: Allocating DMA buffer for non-PCM 2013-02-14 17:52 ` Adrian Knoth @ 2013-02-14 18:01 ` Clemens Ladisch 2013-02-14 18:46 ` Adrian Knoth 0 siblings, 1 reply; 9+ messages in thread From: Clemens Ladisch @ 2013-02-14 18:01 UTC (permalink / raw) To: Adrian Knoth; +Cc: alsa-devel Adrian Knoth wrote: > On Thu, Feb 14, 2013 at 06:46:30PM +0100, Clemens Ladisch wrote: >>> Would you say that the following is the proper way to allocate a DMA >>> buffer used to hold level data? >>> >>> err = snd_dma_alloc_pages(SNDRV_DMA_TYPE_DEV_SG, >>> snd_dma_pci_data(hdspm->pci), >>> MADIFX_LEVEL_BUFFER_SIZE, &hdspm->dmaLevelBuffer); >>> >>> hdspm->level_buffer = snd_sgbuf_get_ptr(&(hdspm->dmaLevelBuffer), 0); >> >> I don't see the code asking for the address of the second page, so I >> guess there isn't one. > > Exactly. So MADIFX_LEVEL_BUFFER_SIZE is guaranteed to not exceed the page size on all architectures? > Just to be sure: Takashi has recommended to use > (u32*)dmaLevelBuffer.area. Even in the case of SG buffers, is this > virtual address continuous and safe for memset? Yes, the SG buffer's pages are vmap()ed there. Regards, Clemens ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: Allocating DMA buffer for non-PCM 2013-02-14 18:01 ` Clemens Ladisch @ 2013-02-14 18:46 ` Adrian Knoth 2013-02-15 9:04 ` Takashi Iwai 0 siblings, 1 reply; 9+ messages in thread From: Adrian Knoth @ 2013-02-14 18:46 UTC (permalink / raw) To: Clemens Ladisch; +Cc: alsa-devel On 02/14/2013 07:01 PM, Clemens Ladisch wrote: >> On Thu, Feb 14, 2013 at 06:46:30PM +0100, Clemens Ladisch wrote: >>>> Would you say that the following is the proper way to allocate a DMA >>>> buffer used to hold level data? >>>> >>>> err = snd_dma_alloc_pages(SNDRV_DMA_TYPE_DEV_SG, >>>> snd_dma_pci_data(hdspm->pci), >>>> MADIFX_LEVEL_BUFFER_SIZE, &hdspm->dmaLevelBuffer); >>>> >>>> hdspm->level_buffer = snd_sgbuf_get_ptr(&(hdspm->dmaLevelBuffer), 0); >>> >>> I don't see the code asking for the address of the second page, so I >>> guess there isn't one. >> >> Exactly. > > So MADIFX_LEVEL_BUFFER_SIZE is guaranteed to not exceed the page size > on all architectures? Absolutely not, it's known to be multiples of the page size, but the purpose of hdspm->level_buffer is to hold the continuous virtual address, so apparently, I was using the wrong getter function in the first place (I was actually looking for .area). The code for accessing the other pages was omitted for the sake of simplicity, but since you've asked, here it is: /* Fill level page table */ for (i = 0; i < MADIFX_NUM_LEVEL_PAGES; i++) { levelPageTable[i] = snd_sgbuf_get_addr(&(hdspm->dmaLevelBuffer), i * MADIFX_HARDWARE_PAGE_SIZE); } /* Write level page table to device */ lpti = (MADIFX == hdspm->io_type) ? MADIFX_LPTI_HMFX : MADIFX_LPTI_MFXT; for (i = 0; i < MADIFX_NUM_LEVEL_PAGES; i++) { madifx_write(hdspm, MADIFX_PAGE_ADDRESS_LIST + (4 * (lpti + i)), levelPageTable[i]); } Cheers ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: Allocating DMA buffer for non-PCM 2013-02-14 18:46 ` Adrian Knoth @ 2013-02-15 9:04 ` Takashi Iwai 0 siblings, 0 replies; 9+ messages in thread From: Takashi Iwai @ 2013-02-15 9:04 UTC (permalink / raw) To: Adrian Knoth; +Cc: alsa-devel, Clemens Ladisch At Thu, 14 Feb 2013 19:46:39 +0100, Adrian Knoth wrote: > > On 02/14/2013 07:01 PM, Clemens Ladisch wrote: > > >> On Thu, Feb 14, 2013 at 06:46:30PM +0100, Clemens Ladisch wrote: > >>>> Would you say that the following is the proper way to allocate a DMA > >>>> buffer used to hold level data? > >>>> > >>>> err = snd_dma_alloc_pages(SNDRV_DMA_TYPE_DEV_SG, > >>>> snd_dma_pci_data(hdspm->pci), > >>>> MADIFX_LEVEL_BUFFER_SIZE, &hdspm->dmaLevelBuffer); > >>>> > >>>> hdspm->level_buffer = snd_sgbuf_get_ptr(&(hdspm->dmaLevelBuffer), 0); > >>> > >>> I don't see the code asking for the address of the second page, so I > >>> guess there isn't one. > >> > >> Exactly. > > > > So MADIFX_LEVEL_BUFFER_SIZE is guaranteed to not exceed the page size > > on all architectures? > > Absolutely not, it's known to be multiples of the page size, but the > purpose of hdspm->level_buffer is to hold the continuous virtual > address, so apparently, I was using the wrong getter function in the > first place (I was actually looking for .area). OK, then disregard my previous comment. The SG-buffer is the right thing. FWIW, snd_sgbuf_get_ptr() return the pointer of the particular page. If you access only the data in the page size, it'll work even with that. Takashi > The code for accessing the other pages was omitted for the sake of > simplicity, but since you've asked, here it is: > > /* Fill level page table */ > for (i = 0; i < MADIFX_NUM_LEVEL_PAGES; i++) { > levelPageTable[i] = snd_sgbuf_get_addr(&(hdspm->dmaLevelBuffer), > i * MADIFX_HARDWARE_PAGE_SIZE); > > } > > /* Write level page table to device */ > lpti = (MADIFX == hdspm->io_type) ? MADIFX_LPTI_HMFX : > MADIFX_LPTI_MFXT; > > for (i = 0; i < MADIFX_NUM_LEVEL_PAGES; i++) { > madifx_write(hdspm, MADIFX_PAGE_ADDRESS_LIST + (4 * (lpti + i)), > levelPageTable[i]); > } > > > > Cheers > _______________________________________________ > Alsa-devel mailing list > Alsa-devel@alsa-project.org > http://mailman.alsa-project.org/mailman/listinfo/alsa-devel > ^ permalink raw reply [flat|nested] 9+ messages in thread
end of thread, other threads:[~2013-02-15 9:04 UTC | newest] Thread overview: 9+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2013-02-14 17:03 Allocating DMA buffer for non-PCM Adrian Knoth 2013-02-14 17:14 ` Takashi Iwai 2013-02-14 17:26 ` Adrian Knoth 2013-02-15 6:22 ` Takashi Iwai 2013-02-14 17:46 ` Clemens Ladisch 2013-02-14 17:52 ` Adrian Knoth 2013-02-14 18:01 ` Clemens Ladisch 2013-02-14 18:46 ` Adrian Knoth 2013-02-15 9:04 ` Takashi Iwai
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