Re: [PATCH] wifi: iwlwifi: pcie: ensure RX_QUEUE_CB_SIZE fits bitfield for gcc-8|9

[David Laight <david.laight.linux@gmail.com>]

On Thu, 12 Jun 2025 21:33:44 +0200
Anders Roxell <anders.roxell@linaro.org> wrote:

> On 2025-06-12 17:21, Johannes Berg wrote:
> > > 
> > > diff --git a/drivers/net/wireless/intel/iwlwifi/pcie/ctxt-info.c b/drivers/net/wireless/intel/iwlwifi/pcie/ctxt-info.c
> > > index cb36baac14da..1854d071aff2 100644
> > > --- a/drivers/net/wireless/intel/iwlwifi/pcie/ctxt-info.c
> > > +++ b/drivers/net/wireless/intel/iwlwifi/pcie/ctxt-info.c
> > > @@ -204,9 +204,10 @@ int iwl_pcie_ctxt_info_init(struct iwl_trans *trans,
> > >  
> > >  	WARN_ON(RX_QUEUE_CB_SIZE(iwl_trans_get_num_rbds(trans)) > 12);
> > >  	control_flags = IWL_CTXT_INFO_TFD_FORMAT_LONG;
> > > -	control_flags |=
> > > -		u32_encode_bits(RX_QUEUE_CB_SIZE(iwl_trans_get_num_rbds(trans)),
> > > -				IWL_CTXT_INFO_RB_CB_SIZE);
> > > +	/* This should just be u32_encode_bits() but gcc-8 and gcc-9 fail to build */
> > > +	control_flags |= FIELD_PREP(IWL_CTXT_INFO_RB_CB_SIZE,
> > > +		RX_QUEUE_CB_SIZE(iwl_trans_get_num_rbds(trans)) &
> > > +		FIELD_MAX(IWL_CTXT_INFO_RB_CB_SIZE));
> > >   
> > 
> > The coding style is really confusing now though - what are arguments to
> > the macro and all that.  
> 
> Would it help if I indent like this?
> 
> diff --git a/drivers/net/wireless/intel/iwlwifi/pcie/ctxt-info.c b/drivers/net/wireless/intel/iwlwifi/pcie/ctxt-info.c
> index cb36baac14da..5bb81ed7db79 100644
> --- a/drivers/net/wireless/intel/iwlwifi/pcie/ctxt-info.c
> +++ b/drivers/net/wireless/intel/iwlwifi/pcie/ctxt-info.c
> @@ -204,9 +204,10 @@ int iwl_pcie_ctxt_info_init(struct iwl_trans *trans,
>  
>  	WARN_ON(RX_QUEUE_CB_SIZE(iwl_trans_get_num_rbds(trans)) > 12);
>  	control_flags = IWL_CTXT_INFO_TFD_FORMAT_LONG;
> -	control_flags |=
> -		u32_encode_bits(RX_QUEUE_CB_SIZE(iwl_trans_get_num_rbds(trans)),
> -				IWL_CTXT_INFO_RB_CB_SIZE);
> +	/* This should just be u32_encode_bits() but gcc-8 and gcc-9 fail to build */
> +	control_flags |= FIELD_PREP(IWL_CTXT_INFO_RB_CB_SIZE,
> +				    RX_QUEUE_CB_SIZE(iwl_trans_get_num_rbds(trans)) &
> +				    FIELD_MAX(IWL_CTXT_INFO_RB_CB_SIZE));

I would always indent the 'continued' part of an arithmetic expression.
Otherwise it looks (in this case) like another argument to FIELD_PREP().
(Not helped by the coding style requiring the '&' on the end of the line
rather than the start of the continuation line.)

	David


>  	control_flags |= u32_encode_bits(rb_size, IWL_CTXT_INFO_RB_SIZE);
>  	ctxt_info->control.control_flags = cpu_to_le32(control_flags);
>  
> 
> Cheers,
> Anders
>