Re: [Intel-wired-lan] [PATCH iwl-net v2] idpf: add missing cpu_to_le32 in idpf_tx_splitq_build_flow_desc

[Willem de Bruijn <willemdebruijn.kernel@gmail.com>]

Marcin Szycik wrote:
> 
> 
> On 03/08/2026 23:06, Willem de Bruijn wrote:
> > From: Willem de Bruijn <willemb@google.com>
> > 
> > idpf_tx_splitq_build_flow_desc performs a 32-bit store to &cmd_dtype
> > to set the 8-bit cmd_dtype and zero the adjacent 3-byte timestamp
> > field in a single operation.
> > 
> > Descriptors are in little endian. Add missing cpu_to_le32 and cast to
> > __le32 to ensure the fields are written correctly also on big endian
> > platforms.
> > 
> > Fixes: 1a49cf814fe1 ("idpf: add Tx timestamp flows")
> > Signed-off-by: Willem de Bruijn <willemb@google.com>
> > Reviewed-by: Tony Nguyen <anthony.l.nguyen@intel.com>
> > 
> > ---
> > 
> > Changes
> >   v1 -> v2
> >   - add Fixes tag, Tony's Reviewed-by and Cc: intel-wired-lan@lists.osuosl.org
> >   v1: https://lore.kernel.org/netdev/20260731103137.4000876-1-willemdebruijn.kernel@gmail.com/
> > ---
> >  drivers/net/ethernet/intel/idpf/idpf_txrx.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/net/ethernet/intel/idpf/idpf_txrx.c b/drivers/net/ethernet/intel/idpf/idpf_txrx.c
> > index c724d429a7aa..91ca75e45463 100644
> > --- a/drivers/net/ethernet/intel/idpf/idpf_txrx.c
> > +++ b/drivers/net/ethernet/intel/idpf/idpf_txrx.c
> > @@ -2408,7 +2408,7 @@ void idpf_tx_splitq_build_flow_desc(union idpf_tx_flex_desc *desc,
> >  				    struct idpf_tx_splitq_params *params,
> >  				    u16 td_cmd, u16 size)
> >  {
> > -	*(u32 *)&desc->flow.qw1.cmd_dtype = (u8)(params->dtype | td_cmd);
> > +	*(__le32 *)&desc->flow.qw1.cmd_dtype = cpu_to_le32((u8)(params->dtype | td_cmd));
> 
> While it technically works, I find it unreadable. Looking at this line
> without reading commit msg, it looks like a bug where a 4-byte value is
> written to u8 field. The intent to zero an adjacent, unrelated field is
> not clear. Consider assigning these 4 fields manually, or adding a
> comment/function doc.

This is a bug fix, which generally should be the smallest surgical
change only.

That said, I do agree on the style, and a follow-up for net-next will
clean that up too:

	@@ -2408,7 +2410,12 @@ void idpf_tx_splitq_build_flow_desc(union idpf_tx_flex_desc *desc,
					    struct idpf_tx_splitq_params *params,
					    u16 td_cmd, u16 size)
	 {
	-       *(__le32 *)&desc->flow.qw1.cmd_dtype = cpu_to_le32((u8)(params->dtype | td_cmd));
	+       desc->flow.qw1.cmd_dtype = (u8)(params->dtype | td_cmd);
	+
	+       desc->flow.qw1.ts[0] = params->offload.desc_ts[0];
	+       desc->flow.qw1.ts[1] = params->offload.desc_ts[1];
	+       desc->flow.qw1.ts[2] = params->offload.desc_ts[2];

The fix is queued. If there is consensus, I can respin. But given that
we will clean this up in net-next properly, my preference is to keep
the minimal fix as is.