linux-kernel - Re: [PATCH 4/8] media: iris: Introduce buffer size calculations for vpu4

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <bee1da42-1108-4d71-a854-e3f76c5a6e96@kernel.org>
Date: Fri, 26 Sep 2025 14:00:06 +0100
From: Bryan O'Donoghue <bod@...nel.org>
To: Vikash Garodia <vikash.garodia@....qualcomm.com>,
 Dikshita Agarwal <dikshita.agarwal@....qualcomm.com>,
 Abhinav Kumar <abhinav.kumar@...ux.dev>,
 Mauro Carvalho Chehab <mchehab@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Philipp Zabel <p.zabel@...gutronix.de>
Cc: linux-arm-msm@...r.kernel.org, linux-media@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 Vishnu Reddy <quic_bvisredd@...cinc.com>
Subject: Re: [PATCH 4/8] media: iris: Introduce buffer size calculations for
 vpu4

On 25/09/2025 00:14, Vikash Garodia wrote:
> +{
> +	u32 dma_opb_wr_tlb_y_size = ((frame_width_coded + 15) >> 4) << 7;
> +	u32 dma_opb_wr_tlb_uv_size = ((frame_width_coded + 15) >> 4) << 7;
> +	u32 dma_opb_wr2_tlb_y_size = ALIGN((2 * 6 * 64 * frame_height_coded / 8), DMA_ALIGNMENT) *
> +					   num_vpp_pipes_enc;
> +	u32 dma_opb_wr2_tlb_uv_size = ALIGN((2 * 6 * 64 * frame_height_coded / 8), DMA_ALIGNMENT) *
> +					    num_vpp_pipes_enc;

I find these calculations pretty nebulous and not very obvious to look at.

A define of some sort with a comment would definitely help other 
programmers reviewing and supporting this code in the future.

(+ 15 >> 4) << 7 - I'm sure it makes sense when you are looking at a 
register spec in front of your eyes but if you don't have that detail 
its pretty hard to say the values are correct.

/*
  * SET_Y_SIZE(x)
  *     - Add 15 because
  *     - Shift 4 to lower nibble because
  *     - Shift the result up 7 because
  */
#define SET_Y_SIZE(x)

---
bod