From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Wolfram Sang <wsa+renesas@sang-engineering.com>
Cc: Linux I2C <linux-i2c@vger.kernel.org>,
Linux-Renesas <linux-renesas-soc@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Wolfram Sang <wsa@the-dreams.de>
Subject: Re: [PATCH 1/4] i2c: add helpers to ease DMA handling
Date: Thu, 15 Jun 2017 22:31:51 +0200 [thread overview]
Message-ID: <CAMuHMdVe1tBMZO9weMsf2Tj7pQ_AUeVu_X=uKbs+JbziLFQHvQ@mail.gmail.com> (raw)
In-Reply-To: <20170615183039.22925-2-wsa+renesas@sang-engineering.com>
Hi Wolfram,
On Thu, Jun 15, 2017 at 8:30 PM, Wolfram Sang
<wsa+renesas@sang-engineering.com> wrote:
> One helper checks if DMA is suitable and optionally creates a bounce
> buffer, if not. The other function returns the bounce buffer and makes
> sure the data is properly copied back to the message.
> --- a/include/linux/i2c.h
> +++ b/include/linux/i2c.h
> @@ -764,6 +767,68 @@ static inline u8 i2c_8bit_addr_from_msg(const struct i2c_msg *msg)
> return (msg->addr << 1) | (msg->flags & I2C_M_RD ? 1 : 0);
> }
>
> +/**
> + * i2c_check_msg_for_dma - check if a message is suitable for DMA
> + * @msg: the message to be checked
> + * @threshold: the amount of byte from which using DMA makes sense
> + * @ptr_for_bounce_buf: if not NULL, a bounce buffer will be attached to this
> + * ptr, if needed. The bounce buffer must be freed by the
> + * caller using i2c_release_bounce_buf().
> + *
> + * Return: -ERANGE if message is smaller than threshold
> + * -EFAULT if message buffer is not DMA capable and no bounce buffer
> + * was requested
> + * -ENOMEM if a bounce buffer could not be created
> + * 0 if message is suitable for DMA
> + *
> + * Note: This function should only be called from process context! It uses
> + * helper functions which work on the 'current' task.
> + */
> +static inline int i2c_check_msg_for_dma(struct i2c_msg *msg, unsigned int threshold,
> + u8 **ptr_for_bounce_buf)
__must_check?
Isn't this function a bit large to be inlined?
> +/**
> + * i2c_release_bounce_buf - copy data back from bounce buffer and release it
> + * @msg: the message to be copied back to
> + * @bounce_buf: the bounce buffer obtained from i2c_check_msg_for_dma().
> + * May be NULL.
> + */
> +static inline void i2c_release_bounce_buf(struct i2c_msg *msg, u8 *bounce_buf)
This one is smaller.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
next prev parent reply other threads:[~2017-06-15 20:31 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-15 18:30 [PATCH 0/4] i2c: document DMA handling and add helpers for it Wolfram Sang
2017-06-15 18:30 ` [PATCH 1/4] i2c: add helpers to ease DMA handling Wolfram Sang
2017-06-15 20:31 ` Geert Uytterhoeven [this message]
2017-06-27 21:16 ` Wolfram Sang
2017-06-15 18:30 ` [PATCH 2/4] i2c: add docs to clarify " Wolfram Sang
2017-06-15 20:30 ` Geert Uytterhoeven
2017-06-15 18:30 ` [PATCH 3/4] i2c: sh_mobile: use helper to decide if DMA is useful Wolfram Sang
2017-06-15 18:30 ` [PATCH 4/4] i2c: rcar: check for DMA-capable buffers Wolfram Sang
2017-06-15 18:48 ` Shuah Khan
2017-06-15 19:17 ` Wolfram Sang
2017-06-15 19:48 ` Shuah Khan
2017-06-15 18:42 ` [PATCH 0/4] i2c: document DMA handling and add helpers for it Wolfram Sang
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