On Thu, Dec 12, 2024 at 05:10:21PM +0530, Dheeraj Reddy Jonnalagadda wrote: > Dear Maintainers, > > I am writing to seek clarification regarding the implementation of the > drm_draw_fill24 function in the DRM subsystem. Specifically, Coverity has > flagged (CID 1602416) the issue in the following line in drm/drm_draw.c > > --> iosys_map_wr(dmap, off + 2, u8, (color & 0x00FF0000) >> 16); > > I have some questions about handling of the color parameter in the function. > > The function currently accepts a u16 value as the color parameter and uses > bitwise operations to extract the RGB components. However, the mask 0x00FF0000 > refers to bits 16–23, which are always zero for a u16 value. Therefore, the > expression (color & 0x00FF0000) will always result in 0. > > Could you please confirm: > > 1. Is the truncation of 32-bit color value to 16 bits the intended behavior? > 2. Alternatively, should the function be updated to accept 32-bit values > as input as the function is called with 32 bit values elsewhere? > > Thank you for your time. Please let me know if further information or context > is required. > > -Dheeraj Dear Maintainers, I am following up on my earlier query regarding the potential issue flagged by Coverity (CID 1602416) in the drm_draw_fill24 function in drm/drm_draw.c. Link to the Coverity issue: https://scan7.scan.coverity.com/#/project-view/52348/11354?selectedIssue=1602416 The action field on Coverity has also been changed to "Fix required" for this issue. To summarize: 1. The color parameter is declared as a u16, but the bitwise operation (color & 0x00FF0000) targets bits that do not exist within a u16 range, effectively always resulting in 0. 2. My query is whether this truncation is intentional or if the function should be updated to accept a 32-bit color value, aligning with its usage elsewhere. I wanted to kindly ask if there has been any decision or additional insight regarding this issue. If needed, I can provide a proposed patch to address the problem once the intended behavior is clarified. Thank you again for your time. -Dheeraj
