From: Robin Murphy <robin.murphy@xxxxxxx>
Date: Wed, 14 Feb 2024 17:20:50 +0000
> On 2024-02-14 4:21 pm, Alexander Lobakin wrote:
[...]
>> -static inline void dma_sync_single_for_cpu(struct device *dev,
>> dma_addr_t addr,
>> - size_t size, enum dma_data_direction dir)
>> +static inline void __dma_sync_single_for_cpu(struct device *dev,
>> + dma_addr_t addr, size_t size, enum dma_data_direction dir)
>
> To me it would feel more logical to put all the wrappers inside the
> #ifdef CONFIG_HAS_DMA and not touch these stubs at all (what does it
> mean to skip an inline no-op?). Or in fact, if dma_skip_sync() is
> constant false for !HAS_DMA, then we could also just make the external
> function declarations unconditional and remove the stubs. Not a critical
> matter though, and I defer to whatever Christoph thinks is most
> maintainable.
It's done like that due to that I'm adding a runtime check in the second
patch. I don't feel like touching this twice makes sense.
[...]
>> @@ -348,18 +348,72 @@ static inline void dma_unmap_single_attrs(struct
>> device *dev, dma_addr_t addr,
>> return dma_unmap_page_attrs(dev, addr, size, dir, attrs);
>> }
>> +static inline void __dma_sync_single_range_for_cpu(struct device *dev,
>> + dma_addr_t addr, unsigned long offset, size_t size,
>> + enum dma_data_direction dir)
>> +{
>> + __dma_sync_single_for_cpu(dev, addr + offset, size, dir);
>> +}
>> +
>> +static inline void __dma_sync_single_range_for_device(struct device
>> *dev,
>> + dma_addr_t addr, unsigned long offset, size_t size,
>> + enum dma_data_direction dir)
>> +{
>> + __dma_sync_single_for_device(dev, addr + offset, size, dir);
>> +}
>
> There is no need to introduce these two.
I already replied to this in the previous thread. Some subsys may want
to check for the shortcut earlier to avoid call ladders of their own
functions. See patch 6 for example where I use this one.
>
>> +
>> +static inline bool dma_skip_sync(const struct device *dev)
>> +{
>> + return !IS_ENABLED(CONFIG_DMA_NEED_SYNC);
>> +}
>> +
>> +static inline bool dma_need_sync(struct device *dev, dma_addr_t
>> dma_addr)
>> +{
>> + return !dma_skip_sync(dev) ? __dma_need_sync(dev, dma_addr) : false;
>> +}
>
> That's a bit of a mind-bender... is it actually just
>
> return !dma_skip_sync(dev) && __dma_need_sync(dev, dma_addr);
Oh, indeed ._.
>
> ?
>
> (I do still think the negative flag makes it all a little harder to
> follow in general than a positive "device needs to consider syncs" flag
> would.)
I think it was in the original Eric's idea and I kept this.
I'm fine with inverting it.
[...]
> Thanks,
> Robin.
Thanks,
Olek
