linux-kernel - Re: [PATCH v2 07/14] mfd: zl3073x: Add components versions register defs

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Message-ID: <46ff3480-caca-4e2c-9382-2897c611758a@redhat.com>
Date: Fri, 11 Apr 2025 15:17:14 +0200
From: Ivan Vecera <ivecera@...hat.com>
To: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: netdev@...r.kernel.org, Vadim Fedorenko <vadim.fedorenko@...ux.dev>,
 Arkadiusz Kubalewski <arkadiusz.kubalewski@...el.com>,
 Jiri Pirko <jiri@...nulli.us>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Prathosh Satish <Prathosh.Satish@...rochip.com>,
 Lee Jones <lee@...nel.org>, Kees Cook <kees@...nel.org>,
 Andy Shevchenko <andy@...nel.org>, Andrew Morton
 <akpm@...ux-foundation.org>, Michal Schmidt <mschmidt@...hat.com>,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-hardening@...r.kernel.org, Andrew Lunn <andrew@...n.ch>
Subject: Re: [PATCH v2 07/14] mfd: zl3073x: Add components versions register
 defs

On 11. 04. 25 1:19 odp., Ivan Vecera wrote:
> The range for regmap 1: (registers 0x000-0x4FF)
> regmap_range_cfg {
>      .range_min = 0,
>      .range_max = 10 * 128 - 1, /* 10 pages, 128 registers each */
>      .selector_reg = 0x7f,      /* page selector at each page */
>      .selector_shift = 0,       /* no shift in page selector */
>      .selector_mask = GENMASK(3, 0),    /* 4 bits for page sel */
>      .window_start = 0,         /* 128 regs from 0x00-0x7f */
>      .window_len = 128,
> };
> 
> The range for regmap 2: (registers 0x500-0x77F)
> regmap_range_cfg {
>      .range_min = 10 * 128,
>      .range_max = 15 * 128 - 1, /* 5 pages, 128 registers each */
>      .selector_reg = 0x7f,      /* page selector at each page */
>      .selector_shift = 0,       /* no shift in page selector */
>      .selector_mask = GENMASK(3, 0),    /* 4 bits for page sel */
>      .window_start = 0,         /* 128 regs from 0x00-0x7f */
>      .window_len = 128,
> };
> 
> Is it now OK?

No this is not good... I cannot use 2 ranges.

This is not safe... if the caller use regmap 2 to read/write something 
below 0x500 (by mistake), no mapping is applied and value is directly 
used as register number that's wrong :-(.

Should I use rather single mapping range to cover all pages and ensure 
at driver level that regmap 2 is not used for regs < 0x500?
-or-
what would be the best approach?

I.