RE: [PATCH] HID: intel-thc-hid: intel-quicki2c: size the input buffer for the DMA

[Xu, Even]

> -----Original Message-----
> From: HyeongJun An <sammiee5311@xxxxxxxxx>
> Sent: Wednesday, August 26, 2026 8:04 PM
> To: Xu, Even <even.xu@xxxxxxxxx>
> Cc: Sun, Xinpeng <xinpeng.sun@xxxxxxxxx>; Jiri Kosina <jikos@xxxxxxxxxx>;
> Benjamin Tissoires <bentiss@xxxxxxxxxx>; linux-input@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; stable@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH] HID: intel-thc-hid: intel-quicki2c: size the input buffer for the
> DMA
> 
> On Wed, Aug 26, 2026 at 10:10 AM Xu, Even <even.xu@xxxxxxxxx> wrote:
> > so it's not a problem, that's why you never reproduce the issue.
> 
> Thanks for the explanation, that clears up the SWDMA side.
> 
> I had read the RxDMA2 side as a separate case, and it looks like I have that wrong
> too.  input_buf is max(max_input_len, SZ_4K) at
> pci-quicki2c.c:607 while THC_RXDMA2 is sized ALIGN(max_input_len, SZ_4K),

Please pay attention, input_buf is HID level software buffer, RxDMA2 uses the hardware DMA buffer which also the same size with SWDMA.

> and LNL leaves qcdev->ddata NULL so the max frame size feature is never
> enabled.  I had assumed that gap was reachable, but you would know whether it
> can be.

If you mention qcdev->ddata, then it's another story, it's a separate HW feature, you can find the detail here: https://docs.kernel.org/hid/intel-thc-hid.html#max-input-size-control
This is a new feature only enabled on PTL/WCL/NVL, so LNL doesn't have it.

> 
> Either way, please drop the patch.  Thanks for taking a look at it.

Also, thanks for your patch!

Best Regards,
Even Xu