linux-kernel - Re: [PATCH v4 16/24] EDAC/amd64: Define function to make space for CS ID

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Date:   Wed, 9 Mar 2022 22:25:22 +0000
From:   Yazen Ghannam <yazen.ghannam@....com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     linux-edac@...r.kernel.org, linux-kernel@...r.kernel.org,
        mchehab@...nel.org, tony.luck@...el.com, james.morse@....com,
        rric@...nel.org, Smita.KoralahalliChannabasappa@....com
Subject: Re: [PATCH v4 16/24] EDAC/amd64: Define function to make space for
 CS ID

On Mon, Feb 14, 2022 at 01:50:54PM +0100, Borislav Petkov wrote:
> On Thu, Jan 27, 2022 at 08:41:07PM +0000, Yazen Ghannam wrote:
> > +static void expand_bits(u8 start_bit, u8 num_bits, u64 *value)
> > +{
> > +	u64 temp1, temp2;
> > +
> > +	if (start_bit == 0) {
> 
> As always
> 
> 	if (!<variable, etc>)
> 
> for 0/NULL tests.
>

Will fix.
 
> > +		*value <<= num_bits;
> > +		return;
> > +	}
> > +
> > +	temp1 = *value & GENMASK_ULL(start_bit - 1, 0);
> > +	temp2 = (*value & GENMASK_ULL(63, start_bit)) << num_bits;
> > +	*value = temp1 | temp2;
> > +}
> > +
> > +static void make_space_for_cs_id_simple(struct addr_ctx *ctx)
> > +{
> > +	u8 num_intlv_bits = ctx->intlv_num_chan;
> > +
> > +	num_intlv_bits += ctx->intlv_num_dies;
> > +	num_intlv_bits += ctx->intlv_num_sockets;
> > +	expand_bits(ctx->intlv_addr_bit, num_intlv_bits, &ctx->ret_addr);
> > +}
> 
> void functions but they return values through their pointer arguments?
> I'm sure you can design those better.
>

I guess this could be "addr = func(x, y, addr)", but why not just operate on
the value directly? There isn't an error condition here that's obvious to me.

Thanks,
Yazen