Messages in this thread | | | From | Oded Gabbay <> | Date | Sun, 23 Jan 2022 18:24:40 +0200 | Subject | Re: [PATCH] habanalabs: Remove unused enum member DMA_SRAM_TO_SRAM |
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On Sun, Jan 23, 2022 at 6:17 PM Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote: > > On Sun, Jan 23, 2022 at 06:11:54PM +0200, Oded Gabbay wrote: > > On Sun, Jan 23, 2022 at 6:08 PM Greg Kroah-Hartman > > <gregkh@linuxfoundation.org> wrote: > > > > > > On Sun, Jan 23, 2022 at 06:01:53PM +0200, Oded Gabbay wrote: > > > > On Sun, Jan 23, 2022 at 5:04 PM Greg Kroah-Hartman > > > > <gregkh@linuxfoundation.org> wrote: > > > > > > > > > > On Sun, Jan 23, 2022 at 04:43:15PM +0200, Oded Gabbay wrote: > > > > > > On Tue, Jan 11, 2022 at 1:47 PM Cai Huoqing <cai.huoqing@linux.dev> wrote: > > > > > > > > > > > > > > The driver don't support the SRAM-to-SRAM translation of DMA, > > > > > > > so remove 'DMA_SRAM_TO_SRAM'. > > > > > > > > > > > > > > Signed-off-by: Cai Huoqing <cai.huoqing@linux.dev> > > > > > > > --- > > > > > > > drivers/misc/habanalabs/include/goya/goya_packets.h | 1 - > > > > > > > 1 file changed, 1 deletion(-) > > > > > > > > > > > > > > diff --git a/drivers/misc/habanalabs/include/goya/goya_packets.h b/drivers/misc/habanalabs/include/goya/goya_packets.h > > > > > > > index ef54bad20509..25fbebdc6143 100644 > > > > > > > --- a/drivers/misc/habanalabs/include/goya/goya_packets.h > > > > > > > +++ b/drivers/misc/habanalabs/include/goya/goya_packets.h > > > > > > > @@ -36,7 +36,6 @@ enum goya_dma_direction { > > > > > > > DMA_SRAM_TO_HOST, > > > > > > > DMA_DRAM_TO_HOST, > > > > > > > DMA_DRAM_TO_DRAM, > > > > > > > - DMA_SRAM_TO_SRAM, > > > > > > > DMA_ENUM_MAX > > > > > > > }; > > > > > > > > > > > > > > -- > > > > > > > 2.25.1 > > > > > > > > > > > > > > > > > > > This is a general spec file in our s/w stack, and therefore a change > > > > > > in it in the driver will cause our driver to be out of sync with our > > > > > > user-space stack. i.e. the value of DMA_ENUM_MAX will be different in > > > > > > the driver and in the user-space stack. I don't know if there will be > > > > > > any consequences but I prefer not to risk it. > > > > > > > > > > If this is synced to userspace, shouldn't it be in a uapi file with a > > > > > specific value associated with it? > > > > > > > > > > thanks, > > > > > > > > > > greg k-h > > > > > > > > Yes, it was a mistake from day 1. A mistake we didn't repeat in future ASICs. > > > > I take great care of putting anything that is synced between driver > > > > and userspace in our uapi file. > > > > > > > > Having said that, after almost 3 years of having this mistake, I feel > > > > it is not too disastrous to leave it as is. > > > > Our Goya s/w stack is pretty much stable and I don't want to make > > > > changes without good reason. > > > > > > You should just move this to a uapi file to show that it is something > > > that can't be changed. Can't you do that without breaking anything on > > > the kernel side? > > On the kernel side there isn't any problem with moving it. > > What I'm afraid of, is that the userspace will now have a duplicate > > definition of this enum. > > Both in the original file, which is included in the user space stack > > from day 1, and from our uapi file. > > In short, I'm afraid of breaking its compilation. > > If you think that's acceptable, I don't have a problem moving it. > > > > > > > > Otherwise maintaining this is going to be hard as no one has a clue that > > > this is a value that userspace uses. > > > > I can document it with a BIG comment in the file. > > And as I said, Goya s/w stack is pretty much fixed and I don't believe > > is going to change anymore. > > The trick is long-term maintaince for the next 20+ years of this code in > the kernel. A huge comment would help, but even better to move this > where it needs to go in a uapi file so that it makes it obvious we can > not change this. > > thanks, > > greg k-h
ok, I'll try to do this internally and see what happens. I'll upstream either the change or a comment, depending on my check.
Oded
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