| Message ID | 20170615183039.22925-2-wsa+renesas@sang-engineering.com |
|---|---|
| State | Superseded |
| Headers | show |
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 -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi Geert, > > +static inline int i2c_check_msg_for_dma(struct i2c_msg *msg, unsigned int threshold, > > + u8 **ptr_for_bounce_buf) > > __must_check? Yes, why not. > Isn't this function a bit large to be inlined? That can be argued, yes. But I am unsure to bloat the core if the function is so rarely needed... > > +static inline void i2c_release_bounce_buf(struct i2c_msg *msg, u8 *bounce_buf) > > This one is smaller. Yup, but of course, they should be put in the same place, whereever that may be. Thanks, Wolfram
diff --git a/include/linux/i2c.h b/include/linux/i2c.h index 72d0ece70ed30d..7204d38eaff07c 100644 --- a/include/linux/i2c.h +++ b/include/linux/i2c.h @@ -33,7 +33,10 @@ #include <linux/rtmutex.h> #include <linux/irqdomain.h> /* for Host Notify IRQ */ #include <linux/of.h> /* for struct device_node */ +#include <linux/slab.h> #include <linux/swab.h> /* for swab16 */ +#include <linux/mm.h> +#include <linux/sched/task_stack.h> #include <uapi/linux/i2c.h> extern struct bus_type i2c_bus_type; @@ -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) +{ + if (ptr_for_bounce_buf) + *ptr_for_bounce_buf = NULL; + + if (msg->len < threshold) + return -ERANGE; + + if (!virt_addr_valid(msg->buf) || object_is_on_stack(msg->buf)) { + pr_debug("msg buffer to 0x%04x is not DMA safe%s\n", msg->addr, + ptr_for_bounce_buf ? ", trying bounce buffer" : ""); + if (ptr_for_bounce_buf) { + if (msg->flags & I2C_M_RD) + *ptr_for_bounce_buf = kzalloc(msg->len, GFP_KERNEL); + else + *ptr_for_bounce_buf = kmemdup(msg->buf, msg->len, + GFP_KERNEL); + if (!*ptr_for_bounce_buf) + return -ENOMEM; + } else { + return -EFAULT; + } + } + + return 0; +} + +/** + * 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) +{ + if (!bounce_buf) + return; + + if (msg->flags & I2C_M_RD) + memcpy(msg->buf, bounce_buf, msg->len); + + kfree(bounce_buf); +} + int i2c_handle_smbus_host_notify(struct i2c_adapter *adap, unsigned short addr); /** * module_i2c_driver() - Helper macro for registering a modular I2C driver