netdev - Re: [RFT][PATCH 4/7] net: dsa: microchip: Remove dev->txbuf

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Date:   Fri, 21 Dec 2018 03:04:36 +0100
From:   Marek Vasut <marex@...x.de>
To:     Tristram.Ha@...rochip.com
Cc:     netdev@...r.kernel.org, Woojung.Huh@...rochip.com, andrew@...n.ch,
        f.fainelli@...il.com
Subject: Re: [RFT][PATCH 4/7] net: dsa: microchip: Remove dev->txbuf

On 12/21/2018 02:02 AM, Tristram.Ha@...rochip.com wrote:
>> On 12/20/2018 10:41 AM, Andrew Lunn wrote:
>>> On Wed, Dec 19, 2018 at 05:20:33PM -0800, Florian Fainelli wrote:
>>>> On 12/19/18 5:06 PM, Marek Vasut wrote:
>>>>> Previous patches unconver that ksz_spi_write() is always ever called
>>>>> with len = 1, 2 or 4. We can thus drop the if (len > SPI_TX_BUF_LEN)
>>>>> check and we can also drop the allocation of the txbuf which is part
>>>>> of the driver data. This wastes 256 bytes for no reason and can be
>>>>> replaced with 8-byte stack allocated buffer, which is what this patch
>>>>> does. This is an intermediate step though, which will go away after
>>>>> regmap conversion.
> 
> The switch uses auto address increment and can return the whole register
> space in 1 transfer.  Most switches have only 256 registers, so I just stopped
> at that number for KSZ9477.
> 
> This read operation is mostly done by users to dump the registers for debugging.
> The write operation can be used to setup registers from a file.
> 
> I mentioned before the driver can use the standard Linux register access API for
> users to read the chip.  Maybe you also want to try that for debugging.

The bulk IO is never used in the driver, ever, so that's not really a
concern. Although, you can use the regmap to read (and write, if you
enable it) registers via debugfs.

-- 
Best regards,
Marek Vasut