On Thu, 16 Jan 2025 at 19:29, Christophe JAILLET <christophe.jaillet@xxxxxxxxxx> wrote: > > >> + z2->tx_buf = devm_kzalloc(dev, sizeof(struct > >> apple_z2_read_interrupt_cmd), GFP_KERNEL); > >> + z2->rx_buf = devm_kzalloc(dev, 4096, GFP_KERNEL); > > > > This will allocate 8192 bytes because of the way the allocator works. > > It needs around 40 bytes for the devm stuff + 4096 requested. So > > rounding rules will allocate 8192 bytes. > > > > So either you could allocate "for free" much more space, or you could > > allocate (and document...) > > z2->rx_buf = devm_kzalloc(dev, 4096 - sizeof(struct devres), > > GFP_KERNEL); > > > > or have an explicit devm_add_action_or_reset() that would require less > > memory, but would add some LoC. > > > > or leave it as-is, of course ;-) > > > > > See https://elixir.bootlin.com/linux/v6.13-rc3/source/drivers/base/ > > devres.c#L97 > > The precise size does not matter in this case, 4096 was picked semi-arbitrarily as a "nice-looking" number that is definitely bigger than the maximum message size.
