netdev - Re: [PATCH net-next v2 3/4] mlxbf_gige: add BlueField-3 Serdes configuration

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Message-ID: <20221116083056.016e3107@kernel.org>
Date:   Wed, 16 Nov 2022 08:30:56 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Saeed Mahameed <saeed@...nel.org>,
        David Thompson <davthompson@...dia.com>
Cc:     Andrew Lunn <andrew@...n.ch>, davem@...emloft.net,
        edumazet@...gle.com, pabeni@...hat.com, netdev@...r.kernel.org,
        cai.huoqing@...ux.dev, brgl@...ev.pl, limings@...dia.com,
        chenhao288@...ilicon.com, huangguangbin2@...wei.com,
        Asmaa Mnebhi <asmaa@...dia.com>
Subject: Re: [PATCH net-next v2 3/4] mlxbf_gige: add BlueField-3 Serdes
 configuration

On Mon, 14 Nov 2022 17:13:05 -0800 Jakub Kicinski wrote:
> On Tue, 15 Nov 2022 02:06:19 +0100 Andrew Lunn wrote:
> > > I don't feel particularly strongly but seems like something worth
> > > exploring. A minor advantage is that once the init is done the tables
> > > can be discarded from memory.    
> > 
> > I wondered about that, but i'm not sure initdata works for modules,
> > and for hot pluggable devices like PCIe, you never know when another
> > one might appear and you need the tables.  
> 
> Right, I meant that the request_firmware() version can discard 
> the tables. I shouldn't have said tables :)

Saeed, David, are you looking into this? The problem come up again 
in a Realtek USB conversation.

The task is so small and well defined I'm pretty sure I can get some
aspiring kernel developer at Meta to knock it off in a few days.

FWIW the structure of a file I had in mind would be something like this:

# Section 0 - strings (must be section 0)
 # header
 u32 type:   1   # string section
 u32 length: n   # length excluding header and pads
 u32 name:   0   # offset to the name in str section
 u32 pad:    0   # align to 8B
 # data
 .str\0table_abc\0table_def\0some_other_string\0
 # pad, align to 8B
 \0\0\0\0\0\0\0

# Section 1 - table_abc
 # header
 u32 type:   2   # 32b/32b table
 u32 length: 64  # length excluding header and pads
 u32 name:   5   # offset to the name in str section
 u32 pad:    0
 # data
 [ 0x210, 0xc00ff ]
 [ 0x214, 0xffeee ]
 [ 0x218, 0xdeaddd ]
 [ 0x21c, 0xc4ee5e ]
 [ 0x220, 0xc00ff ]
 [ 0x224, 0xffeee ]
 [ 0x228, 0xdeaddd ]
 [ 0x22c, 0xc4ee5e ]

etc.

Use:
	struct fw_table32 *abc, *def;

	fw = request_firmware("whatever_name.ftb");
	
	abc = fw_table_get(fw, "table_abc");
	/* use abc */

	def = fw_table_get(fw, "table_def");
	/* use def */

	release_firmware(fw)