linux-kernel - Re: [RFC net-next 15/15] net: lora: Add Semtech SX1301

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Message-ID: <20180702161258.GA18744@sirena.org.uk>
Date:   Mon, 2 Jul 2018 17:12:58 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Andreas Färber <afaerber@...e.de>
Cc:     netdev@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org,
        Jian-Hong Pan <starnight@...cu.edu.tw>,
        Jiri Pirko <jiri@...nulli.us>,
        Marcel Holtmann <marcel@...tmann.org>,
        "David S . Miller" <davem@...emloft.net>,
        Matthias Brugger <mbrugger@...e.com>,
        Janus Piwek <jpiwek@...oweurope.com>,
        Michael Röder <michael.roeder@...et.eu>,
        Dollar Chen <dollar.chen@...ec.com>,
        Ken Yu <ken.yu@...wireless.com>,
        Ben Whitten <ben.whitten@...rdtech.com>,
        Steve deRosier <derosier@...il.com>, linux-spi@...r.kernel.org
Subject: Re: [RFC net-next 15/15] net: lora: Add Semtech SX1301

On Sun, Jul 01, 2018 at 01:08:04PM +0200, Andreas Färber wrote:

> +static void sx1301_radio_spi_set_cs(struct spi_device *spi, bool enable)
> +{
> +	int ret;
> +
> +	dev_dbg(&spi->dev, "setting SPI CS to %s\n", enable ? "1" : "0");
> +
> +	if (enable)
> +		return;
> +
> +	ret = sx1301_radio_set_cs(spi->controller, enable);
> +	if (ret)
> +		dev_warn(&spi->dev, "failed to write CS (%d)\n", ret);
> +}

So we never disable chip select?

> +	if (tx_buf) {
> +		ret = sx1301_write(ssx->parent, ssx->regs + REG_RADIO_X_ADDR, tx_buf ? tx_buf[0] : 0);

This looks confused.  We're in an if (tx_buf) block but there's a use of
the ternery operator that appears to be checking if we have a tx_buf?

> +		if (ret) {
> +			dev_err(&spi->dev, "SPI radio address write failed\n");
> +			return ret;
> +		}
> +
> +		ret = sx1301_write(ssx->parent, ssx->regs + REG_RADIO_X_DATA, (tx_buf && xfr->len >= 2) ? tx_buf[1] : 0);
> +		if (ret) {
> +			dev_err(&spi->dev, "SPI radio data write failed\n");
> +			return ret;
> +		}

This looks awfully like you're coming in at the wrong abstraction layer
and the hardware actually implements a register abstraction rather than
a SPI one so you should be using regmap as the abstraction.

> +	if (rx_buf) {
> +		ret = sx1301_read(ssx->parent, ssx->regs + REG_RADIO_X_DATA_READBACK, &rx_buf[xfr->len - 1]);
> +		if (ret) {
> +			dev_err(&spi->dev, "SPI radio data read failed\n");
> +			return ret;
> +		}
> +	}

For a read we never set an address?

> +static void sx1301_radio_setup(struct spi_controller *ctrl)
> +{
> +	ctrl->mode_bits = SPI_CS_HIGH | SPI_NO_CS;

This controller has no chip select but we provided a set_cs operation?

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