linux-kernel - [PATCH v2 13/15] power: supply: bd71828: Support wider register addresses

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Message-ID: <a590dac57dab146d43d7e57b396a9ccdc91311a6.1761564043.git.mazziesaccount@gmail.com>
Date: Mon, 27 Oct 2025 13:48:04 +0200
From: Matti Vaittinen <mazziesaccount@...il.com>
To: Matti Vaittinen <mazziesaccount@...il.com>,
	Matti Vaittinen <matti.vaittinen@...rohmeurope.com>
Cc: Lee Jones <lee@...nel.org>, Pavel Machek <pavel@...nel.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Sebastian Reichel <sre@...nel.org>,
	Liam Girdwood <lgirdwood@...il.com>,
	Mark Brown <broonie@...nel.org>,
	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...nel.org>,
	Matti Vaittinen <mazziesaccount@...il.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Bartosz Golaszewski <brgl@...ev.pl>,
	Andreas Kemnade <andreas@...nade.info>,
	Alexandre Belloni <alexandre.belloni@...tlin.com>,
	linux-leds@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	linux-clk@...r.kernel.org, linux-gpio@...r.kernel.org,
	linux-rtc@...r.kernel.org
Subject: [PATCH v2 13/15] power: supply: bd71828: Support wider register
 addresses

The BD71828 power-supply driver assumes register addresses to be 8-bit.
The new BD72720 will use stacked register maps to hide paging which is
done using secondary I2C slave address. This requires use of 9-bit
register addresses in the power-supply driver (added offset 0x100 to
the 8-bit hardware register addresses).

The cost is slightly used memory consumption as the members in the
struct pwr_regs will be changed from u8 to unsigned int, which means 3
byte increase / member / instance.
This is currently 14 members (expected to possibly be increased when
adding new variants / new functionality which may introduce new
registers, but not expected to grow much) and 2 instances (will be 3
instances when BD72720 gets added).

So, even if the number of registers grew to 50 it'd be 150 bytes /
instance. Assuming we eventually supported 5 variants, it'd be
5 * 150 bytes, which stays very reasonable considering systems we are
dealing with.

As a side note, we can reduce the "wasted space / member / instance" from
3 bytes to 1 byte, by using u16 instead of the unsigned int if needed. I
rather use unsigned int to be initially prepared for devices with 32 bit
registers if there is no need to count bytes.

Signed-off-by: Matti Vaittinen <mazziesaccount@...il.com>
---
Revision history:
 RFCv1 => v2:
 - New patch
---
 drivers/power/supply/bd71828-power.c | 26 +++++++++++++-------------
 1 file changed, 13 insertions(+), 13 deletions(-)

diff --git a/drivers/power/supply/bd71828-power.c b/drivers/power/supply/bd71828-power.c
index f667baedeb77..ce73c0f48397 100644
--- a/drivers/power/supply/bd71828-power.c
+++ b/drivers/power/supply/bd71828-power.c
@@ -44,19 +44,19 @@
 #define VBAT_LOW_TH			0x00D4

 struct pwr_regs {
-	u8 vbat_avg;
-	u8 ibat;
-	u8 ibat_avg;
-	u8 btemp_vth;
-	u8 chg_state;
-	u8 bat_temp;
-	u8 dcin_stat;
-	u8 dcin_collapse_limit;
-	u8 chg_set1;
-	u8 chg_en;
-	u8 vbat_alm_limit_u;
-	u8 conf;
-	u8 vdcin;
+	unsigned int vbat_avg;
+	unsigned int ibat;
+	unsigned int ibat_avg;
+	unsigned int btemp_vth;
+	unsigned int chg_state;
+	unsigned int bat_temp;
+	unsigned int dcin_stat;
+	unsigned int dcin_collapse_limit;
+	unsigned int chg_set1;
+	unsigned int chg_en;
+	unsigned int vbat_alm_limit_u;
+	unsigned int conf;
+	unsigned int vdcin;
 };

 static const struct pwr_regs pwr_regs_bd71828 = {
-- 
2.51.0

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