Re: [PATCH] spi: add ch341a usb2spi driver

[Johannes Thumshirn]

On 05/07/2024 19:41, Mark Brown wrote:
> > +config SPI_CH341
> > +	tristate "CH341 USB2SPI adapter"
> > +	depends on SPI_MASTER && USB
> > +	help
> > +	  Enables the SPI controller on the CH341a USB to serial chip
> > +
> >   #
> >   # Add new SPI master controllers in alphabetical order above this line
> >   #
>
> Like the comment says please keep these files sorted (I appreciate
> there's some things been missed).

Oops. Fixed, sorry.

> > +++ b/drivers/spi/spi-ch341.c
> > @@ -0,0 +1,236 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * QiHeng Electronics ch341a USB-to-SPI adapter driver
> > + *
> > + * Copyright (C) 2024 Johannes Thumshirn <jth@xxxxxxxxxx>
>
> Please make the entire comment block a C++ one so things look clearer.

I've never seen that in kernel code, but sure changed it.

> > +static void ch341_set_cs(struct spi_device *spi, bool is_high)
> > +{
> > +	struct ch341_spi_dev *ch341 =
> > +		spi_controller_get_devdata(spi->controller);
> > +
> > +	memset(ch341->tx_buf, 0, CH341_PACKET_LENGTH);
> > +	ch341->tx_buf[0] = CH341A_CMD_UIO_STREAM;
> > +	ch341->tx_buf[1] = CH341A_CMD_UIO_STM_OUT | (is_high ? 0x36 : 0x37);
> > +
> > +	if (is_high) {
> > +		ch341->tx_buf[2] = CH341A_CMD_UIO_STM_DIR | 0x3f;
> > +		ch341->tx_buf[3] = CH341A_CMD_UIO_STM_END;
> > +	} else {
> > +		ch341->tx_buf[2] = CH341A_CMD_UIO_STM_END;
> > +	}
> > +
> > +	(void)usb_bulk_msg(ch341->udev, ch341->write_pipe, ch341->tx_buf,
> > +			   (is_high ? 4 : 3), NULL, CH341_DEFAULT_TIMEOUT);
>
> The cast to void here is very suspicious, what's it doing?

Explicitly ignoring errors from usb_bulk_msg() as ->set_cs() can't 
really handle error returns.

I've changed it to an error print.


> > +static int ch341_config_stream(struct ch341_spi_dev *ch341, int speed)
> > +{
> > +	memset(ch341->tx_buf, 0, CH341_PACKET_LENGTH);
> > +	ch341->tx_buf[0] = CH341A_CMD_I2C_STREAM;
> > +	ch341->tx_buf[1] = CH341A_CMD_I2C_STM_SET | (speed & 0x7);
> > +	ch341->tx_buf[2] = CH341A_CMD_I2C_STM_END;
> > +
> > +	return usb_bulk_msg(ch341->udev, ch341->write_pipe, ch341->tx_buf, 3,
> > +			    NULL, CH341_DEFAULT_TIMEOUT);
>
> No validation of speed?

TBH I haven't found a command that reads the current settings of the device.

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