netdev - Re: [RFC PATCH V2 net-next 03/11] net: hibmcge: Add mdio and hardware configuration supported in this module

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Message-ID: <79122634-093b-44a3-bbcd-479d6692affc@lunn.ch>
Date: Fri, 16 Aug 2024 04:25:39 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Jijie Shao <shaojijie@...wei.com>
Cc: yisen.zhuang@...wei.com, salil.mehta@...wei.com, davem@...emloft.net,
	edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
	horms@...nel.org, shenjian15@...wei.com, wangpeiyang1@...wei.com,
	liuyonglong@...wei.com, sudongming1@...wei.com,
	xujunsheng@...wei.com, shiyongbang@...wei.com, jdamato@...tly.com,
	jonathan.cameron@...wei.com, shameerali.kolothum.thodi@...wei.com,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH V2 net-next 03/11] net: hibmcge: Add mdio and
 hardware configuration supported in this module

> +static int hbg_mdio_cmd_send(struct hbg_mac *mac, u32 prt_addr, u32 dev_addr,
> +			     u32 type, u32 op_code)
> +{
> +	struct hbg_mdio_command mdio_cmd;
> +
> +	hbg_mdio_get_command(mac, &mdio_cmd);
> +	mdio_cmd.mdio_st = type;
> +	/* if auto scan enabled, this value need fix to 0 */
> +	mdio_cmd.mdio_start = 0x1;
> +	mdio_cmd.mdio_op = op_code;
> +	mdio_cmd.mdio_prtad = prt_addr;
> +	mdio_cmd.mdio_devad = dev_addr;
> +	hbg_mdio_set_command(mac, &mdio_cmd);
> +
> +	/* wait operation complete and check the result */
> +	return hbg_mdio_check_send_result(mac);

> +struct hbg_mdio_command {
> +	union {
> +		struct {
> +			u32 mdio_devad : 5;
> +			u32 mdio_prtad :5;
> +			u32 mdio_op : 2;
> +			u32 mdio_st : 2;
> +			u32 mdio_start : 1;
> +			u32 mdio_clk_sel : 1;
> +			u32 mdio_auto_scan : 1;
> +			u32 mdio_clk_sel_exp : 1;
> +			u32 rev : 14;
> +		};
> +		u32 bits;
> +	};
> +};

This is generally not the way to do this. Please look at the macros in
include/linux/bitfield.h. FIELD_PREP, GENMASK, BIT, FIELD_GET
etc. These are guaranteed to work for both big and little endian, and
you avoid issues where the compiler decides to add padding in your
bitfields.

	Andrew