linux-kernel - Re: [PATCH RFC 3/6] dmaengine: qcom: gpi: Accept protocol ID hints

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Message-ID: <e0886f9e-bcc1-48dc-a175-2147d8d4fc3e@oss.qualcomm.com>
Date: Sat, 2 Aug 2025 14:39:48 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Geert Uytterhoeven <geert@...ux-m68k.org>,
        Konrad Dybcio <konradybcio@...nel.org>
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Subject: Re: [PATCH RFC 3/6] dmaengine: qcom: gpi: Accept protocol ID hints

On 7/30/25 1:32 PM, Geert Uytterhoeven wrote:
> Hi Konrad,
> 
> On Wed, 30 Jul 2025 at 11:35, Konrad Dybcio <konradybcio@...nel.org> wrote:
>> From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
>>
>> Client drivers may now pass hints to dmaengine drivers. GPI DMA's only
>> consumers (GENI SEs) need to pass a protocol (I2C, I3C, SPI, etc.) ID
>> to the DMA engine driver, for it to take different actions.
>>
>> Currently, that's done through passing that ID through device tree,
>> with each Serial Engine expressed NUM_PROTOCOL times, resulting in
>> terrible dt-bindings that are full of useless copypasta.
>>
>> To help get rid of that, accept the driver cookie instead, while
>> keeping backwards compatibility.
>>
>> Signed-off-by: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
> 
> Thanks for your patch!
> 
>> --- a/drivers/dma/qcom/gpi.c
>> +++ b/drivers/dma/qcom/gpi.c
>> @@ -2145,7 +2151,8 @@ static struct dma_chan *gpi_of_dma_xlate(struct of_phandle_args *args,
>>         }
>>
>>         gchan->seid = seid;
>> -       gchan->protocol = args->args[2];
>> +       /* The protocol ID is in the teens range, simply ignore the higher bits */
>> +       gchan->protocol = (u32)((u64)proto);
> 
> A single cast "(uintptr_t)" should be sufficient.
> Casing the pointer to u64 on 32-bit may trigger:
> 
>     warning: cast from pointer to integer of different size
> [-Wpointer-to-int-cast]

Good point, not compiling for 32-bit always ends up biting.. thanks

Konrad