linux-kernel - Re: [PATCH 1/2] i2c: tegra: Maintain CPU endianness

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Message-ID: <20150122074001.GB427@ulmo>
Date:	Thu, 22 Jan 2015 08:40:02 +0100
From:	Thierry Reding <thierry.reding@...il.com>
To:	Dmitry Osipenko <digetx@...il.com>
Cc:	Wolfram Sang <wsa@...-dreams.de>,
	Stephen Warren <swarren@...dotorg.org>,
	Alexandre Courbot <gnurou@...il.com>,
	Laxman Dewangan <ldewangan@...dia.com>,
	Ben Dooks <ben.dooks@...ethink.co.uk>,
	Bob Mottram <bob.mottram@...ethink.co.uk>,
	linux-tegra@...r.kernel.org, linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] i2c: tegra: Maintain CPU endianness

On Tue, Jan 20, 2015 at 03:22:25PM +0300, Dmitry Osipenko wrote:
> Support CPU BE mode by adding endianness conversion for memcpy interactions.
> 
> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> ---
>  drivers/i2c/busses/i2c-tegra.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
> index 28b87e6..e0d3ef1 100644
> --- a/drivers/i2c/busses/i2c-tegra.c
> +++ b/drivers/i2c/busses/i2c-tegra.c
> @@ -286,6 +286,7 @@ static int tegra_i2c_empty_rx_fifo(struct tegra_i2c_dev *i2c_dev)
>  	if (rx_fifo_avail > 0 && buf_remaining > 0) {
>  		BUG_ON(buf_remaining > 3);
>  		val = i2c_readl(i2c_dev, I2C_RX_FIFO);
> +		val = cpu_to_le32(val);

Should this not technically be le32_to_cpu() since the data originates
from the I2C controller?

>  		memcpy(buf, &val, buf_remaining);
>  		buf_remaining = 0;
>  		rx_fifo_avail--;
> @@ -343,7 +344,9 @@ static int tegra_i2c_fill_tx_fifo(struct tegra_i2c_dev *i2c_dev)
>  	 */
>  	if (tx_fifo_avail > 0 && buf_remaining > 0) {
>  		BUG_ON(buf_remaining > 3);
> +		val = 0;

Why does this have to be initialized to 0 now?

Thierry

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