On Mon, Mar 30, 2026 at 9:29 PM Andy Shevchenko <[email protected]> wrote: > > On Mon, Mar 30, 2026 at 11:41 PM Rosen Penev <[email protected]> wrote: > > On Mon, Mar 30, 2026 at 1:46 AM Andy Shevchenko > > <[email protected]> wrote: > > > On Sat, Mar 28, 2026 at 9:17 PM Rosen Penev <[email protected]> wrote: > > ... > > > > > - hsu = devm_kzalloc(chip->dev, sizeof(*hsu), GFP_KERNEL); > > > > + /* Calculate nr_channels from the IO space length */ > > > > + nr_channels = (chip->length - chip->offset) / > > > > HSU_DMA_CHAN_LENGTH; > > > > + hsu = devm_kzalloc(chip->dev, struct_size(hsu, chan, > > > > nr_channels), GFP_KERNEL); > > > > if (!hsu) > > > > return -ENOMEM; > > > > > > > > - chip->hsu = hsu; > > > > - > > > > - /* Calculate nr_channels from the IO space length */ > > > > - hsu->nr_channels = (chip->length - chip->offset) / > > > > HSU_DMA_CHAN_LENGTH; > > > > + hsu->nr_channels = nr_channels; > > > > > > > > - hsu->chan = devm_kcalloc(chip->dev, hsu->nr_channels, > > > > - sizeof(*hsu->chan), GFP_KERNEL); > > > > - if (!hsu->chan) > > > > - return -ENOMEM; > > > > + chip->hsu = hsu; > > > > > > Don't know these _flex() APIs enough, but can we leave the chip->hsu = > > > hsu; in the same place as it's now? > > __counted_by requires the first assignment after allocation to be the > > counting variable. The _flex macros do this automatically for GCC15 > > and above. > > Why? The hsu member has nothing to do with VLA, where is this > requirement coming from? My understanding is that the check should > imply the minimum sizeof of the data structure and the compiler should > know that way before doing any allocations. Not sure I follow. This patch changes hsu's chan member to a FAM. Where is VLA coming from?
The current code is devm_kzalloc(x, struct_size()). When it gets introduced, I'm sure there will be a treewide conversion to devm_kzalloc_flex, which would automatically set the counting variable for >=GCC15. It's best practice to assign right after since kzalloc_flex does it anyways. > > My understanding seems in align with what Gustavo blogged: > https://people.kernel.org/gustavoars/how-to-use-the-new-counted_by-attribute-in-c-and-linux > > The same is written in the GCC patch description > https://gcc.gnu.org/pipermail/gcc-patches/2024-May/653123.html > > -- > With Best Regards, > Andy Shevchenko
