Re: [PATCH v2] staging: sm750fb: fix mono image source stride mismatch in lynxfb_ops_imageblit()

[Dan Carpenter]

On Sat, Jul 18, 2026 at 03:31:03PM +0500, Muhammad Bilal wrote:
> sm750_hw_imageblit() advances its monochrome source pointer by
> src_delta per scanline, and computes the correct rounded-up stride
> internally as:
> 
> 	bytes_per_scan = (width + start_bit + 7) / 8;
> 
> Its only caller, lynxfb_ops_imageblit(), instead passed src_delta as
> image->width >> 3. For widths not a multiple of 8 this under-counted
> the stride, so the source pointer fell further behind the real
> per-scanline layout on every line, corrupting the rendered image.
> 
> Rather than just fixing the caller's calculation, remove src_delta
> as a parameter entirely and have sm750_hw_imageblit() advance by the
> bytes_per_scan it already computes for itself. There has only ever
> been one caller, and that caller was passing an out-of-sync
> derivative of the same width/start_bit values sm750_hw_imageblit()
> already has, so keeping stride as a separate parameter served no
> purpose beyond letting the two calculations drift apart, which is
> exactly what happened here.
> 
> Fixes: 81dee67e215b2 ("staging: sm750fb: add sm750 to staging")
> Signed-off-by: Muhammad Bilal <meatuni001@xxxxxxxxx>
> ---

There is supposed to be a little note here:
---
v2: Added a Fixes tag.

https://staticthinking.wordpress.com/2022/07/27/how-to-send-a-v2-patch/

Obviously there is an inconsistency between rounding up and down
but without testing it's less clear which one is correct...

regards,
dan carpenter