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Date: Wed, 6 Mar 2024 14:40:55 +0100
From: Andrew Lunn <andrew@lunn.ch>
To: Parthiban Veerasooran <Parthiban.Veerasooran@microchip.com>
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Subject: Re: [PATCH net-next v3 02/12] net: ethernet: oa_tc6: implement
 register write operation
Message-ID: <43f49aff-ca74-4d10-a478-89ea7497ba83@lunn.ch>
References: <20240306085017.21731-1-Parthiban.Veerasooran@microchip.com>
 <20240306085017.21731-3-Parthiban.Veerasooran@microchip.com>
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In-Reply-To: <20240306085017.21731-3-Parthiban.Veerasooran@microchip.com>

> +config OA_TC6
> +	tristate "OPEN Alliance TC6 10BASE-T1x MAC-PHY support"
> +	depends on SPI
> +	select PHYLIB
> +	help
> +	  This library implements OPEN Alliance TC6 10BASE-T1x MAC-PHY
> +	  Serial Interface protocol for supporting 10BASE-T1x MAC-PHYs.
> +
> +	  To know the implementation details, refer documentation in
> +	  <file:Documentation/networking/oa-tc6-framework.rst>.
> +
> +	  This option is provided for the case where no in-kernel-tree modules
> +	  require OA_TC6 functions, but a module built outside the kernel tree
> +	  does. Such modules that use library OA_TC6 functions require M here.

We generally don't refer to out of tree modules. We know they exist,
but we don't take any steps to support them, the internal APIs are not
fixed etc. So i would drop this last paragraph.

> +static int oa_tc6_check_ctrl_write_reply(struct oa_tc6 *tc6, u8 size)
> +{
> +	u8 *tx_buf = tc6->spi_ctrl_tx_buf;
> +	u8 *rx_buf = tc6->spi_ctrl_rx_buf;
> +
> +	rx_buf += OA_TC6_CTRL_IGNORED_SIZE;
> +
> +	/* The echoed control write must match with the one that was
> +	 * transmitted.
> +	 */
> +	if (memcmp(tx_buf, rx_buf, size - OA_TC6_CTRL_IGNORED_SIZE))
> +		return -ENODEV;
> +

I think EPROTO or EIO would be better. The device might have crashed,
burned and is gone, but isn't a bit flip on the SPI bus more likely?

       Andrew