[v3,3/3] i2c: smbus: switch from loops to memcpy
diff mbox series

Message ID 20191112203132.163306-4-dmitry.torokhov@gmail.com
State Under Review
Headers show
Series
  • Use void pointers instead of char in I2C transfer APIs
Related show

Commit Message

Dmitry Torokhov Nov. 12, 2019, 8:31 p.m. UTC
When copying memory from one buffer to another, instead of open-coding
loops with byte-by-byte copies let's use memcpy() which might be a bit
faster and makes intent more clear.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

---

Changes in v3:
- new patch using memcpy() for moving data around

 drivers/i2c/i2c-core-smbus.c | 15 +++++----------
 1 file changed, 5 insertions(+), 10 deletions(-)

Comments

Luca Ceresoli Nov. 13, 2019, 9:47 a.m. UTC | #1
Hi Dmitry,

On 12/11/19 21:31, Dmitry Torokhov wrote:
> When copying memory from one buffer to another, instead of open-coding
> loops with byte-by-byte copies let's use memcpy() which might be a bit
> faster and makes intent more clear.

Good idea!

Reviewed-by: Luca Ceresoli <luca@lucaceresoli.net>
Uwe Kleine-König Nov. 18, 2019, 7:47 a.m. UTC | #2
Hello Dmitry,

On Tue, Nov 12, 2019 at 12:31:32PM -0800, Dmitry Torokhov wrote:
> When copying memory from one buffer to another, instead of open-coding
> loops with byte-by-byte copies let's use memcpy() which might be a bit
> faster and makes intent more clear.
> 
> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
> 
> ---
> 
> Changes in v3:
> - new patch using memcpy() for moving data around
> 
>  drivers/i2c/i2c-core-smbus.c | 15 +++++----------
>  1 file changed, 5 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/i2c/i2c-core-smbus.c b/drivers/i2c/i2c-core-smbus.c
> index 7b4e2270eeda1..bbafdd3b1b114 100644
> --- a/drivers/i2c/i2c-core-smbus.c
> +++ b/drivers/i2c/i2c-core-smbus.c
> @@ -397,8 +397,7 @@ static s32 i2c_smbus_xfer_emulated(struct i2c_adapter *adapter, u16 addr,
>  			}
>  
>  			i2c_smbus_try_get_dmabuf(&msg[0], command);
> -			for (i = 1; i < msg[0].len; i++)
> -				msg[0].buf[i] = data->block[i - 1];
> +			memcpy(msg[0].buf + 1, data->block, msg[0].len - 1);

Can it happen that msg[0].len is zero?

>  		}
>  		break;
>  	case I2C_SMBUS_BLOCK_PROC_CALL:

Best regards
Uwe
Dmitry Torokhov Nov. 18, 2019, 8:09 a.m. UTC | #3
On Mon, Nov 18, 2019 at 08:47:57AM +0100, Uwe Kleine-König wrote:
> Hello Dmitry,
> 
> On Tue, Nov 12, 2019 at 12:31:32PM -0800, Dmitry Torokhov wrote:
> > When copying memory from one buffer to another, instead of open-coding
> > loops with byte-by-byte copies let's use memcpy() which might be a bit
> > faster and makes intent more clear.
> > 
> > Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
> > 
> > ---
> > 
> > Changes in v3:
> > - new patch using memcpy() for moving data around
> > 
> >  drivers/i2c/i2c-core-smbus.c | 15 +++++----------
> >  1 file changed, 5 insertions(+), 10 deletions(-)
> > 
> > diff --git a/drivers/i2c/i2c-core-smbus.c b/drivers/i2c/i2c-core-smbus.c
> > index 7b4e2270eeda1..bbafdd3b1b114 100644
> > --- a/drivers/i2c/i2c-core-smbus.c
> > +++ b/drivers/i2c/i2c-core-smbus.c
> > @@ -397,8 +397,7 @@ static s32 i2c_smbus_xfer_emulated(struct i2c_adapter *adapter, u16 addr,
> >  			}
> >  
> >  			i2c_smbus_try_get_dmabuf(&msg[0], command);
> > -			for (i = 1; i < msg[0].len; i++)
> > -				msg[0].buf[i] = data->block[i - 1];
> > +			memcpy(msg[0].buf + 1, data->block, msg[0].len - 1);
> 
> Can it happen that msg[0].len is zero?

No, it can not, because of the "msg[0].len = data->block[0] + 2;" line
above.

Thanks.
Uwe Kleine-König Nov. 18, 2019, 8:47 a.m. UTC | #4
On Mon, Nov 18, 2019 at 12:09:39AM -0800, Dmitry Torokhov wrote:
> On Mon, Nov 18, 2019 at 08:47:57AM +0100, Uwe Kleine-König wrote:
> > Hello Dmitry,
> > 
> > On Tue, Nov 12, 2019 at 12:31:32PM -0800, Dmitry Torokhov wrote:
> > > When copying memory from one buffer to another, instead of open-coding
> > > loops with byte-by-byte copies let's use memcpy() which might be a bit
> > > faster and makes intent more clear.
> > > 
> > > Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
> > > 
> > > ---
> > > 
> > > Changes in v3:
> > > - new patch using memcpy() for moving data around
> > > 
> > >  drivers/i2c/i2c-core-smbus.c | 15 +++++----------
> > >  1 file changed, 5 insertions(+), 10 deletions(-)
> > > 
> > > diff --git a/drivers/i2c/i2c-core-smbus.c b/drivers/i2c/i2c-core-smbus.c
> > > index 7b4e2270eeda1..bbafdd3b1b114 100644
> > > --- a/drivers/i2c/i2c-core-smbus.c
> > > +++ b/drivers/i2c/i2c-core-smbus.c
> > > @@ -397,8 +397,7 @@ static s32 i2c_smbus_xfer_emulated(struct i2c_adapter *adapter, u16 addr,
> > >  			}
> > >  
> > >  			i2c_smbus_try_get_dmabuf(&msg[0], command);
> > > -			for (i = 1; i < msg[0].len; i++)
> > > -				msg[0].buf[i] = data->block[i - 1];
> > > +			memcpy(msg[0].buf + 1, data->block, msg[0].len - 1);
> > 
> > Can it happen that msg[0].len is zero?
> 
> No, it can not, because of the "msg[0].len = data->block[0] + 2;" line
> above.

OK, and as passing data with data->block[0] = 254 also makes the code do
strange things already without your patch. I now also checked the other
conversions for similar problems and didn't find any. So:

Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

Best regards
Uwe

Patch
diff mbox series

diff --git a/drivers/i2c/i2c-core-smbus.c b/drivers/i2c/i2c-core-smbus.c
index 7b4e2270eeda1..bbafdd3b1b114 100644
--- a/drivers/i2c/i2c-core-smbus.c
+++ b/drivers/i2c/i2c-core-smbus.c
@@ -397,8 +397,7 @@  static s32 i2c_smbus_xfer_emulated(struct i2c_adapter *adapter, u16 addr,
 			}
 
 			i2c_smbus_try_get_dmabuf(&msg[0], command);
-			for (i = 1; i < msg[0].len; i++)
-				msg[0].buf[i] = data->block[i - 1];
+			memcpy(msg[0].buf + 1, data->block, msg[0].len - 1);
 		}
 		break;
 	case I2C_SMBUS_BLOCK_PROC_CALL:
@@ -413,8 +412,7 @@  static s32 i2c_smbus_xfer_emulated(struct i2c_adapter *adapter, u16 addr,
 
 		msg[0].len = data->block[0] + 2;
 		i2c_smbus_try_get_dmabuf(&msg[0], command);
-		for (i = 1; i < msg[0].len; i++)
-			msg[0].buf[i] = data->block[i - 1];
+		memcpy(msg[0].buf + 1, data->block, msg[0].len - 1);
 
 		msg[1].flags |= I2C_M_RECV_LEN;
 		msg[1].len = 1; /* block length will be added by
@@ -436,8 +434,7 @@  static s32 i2c_smbus_xfer_emulated(struct i2c_adapter *adapter, u16 addr,
 			msg[0].len = data->block[0] + 1;
 
 			i2c_smbus_try_get_dmabuf(&msg[0], command);
-			for (i = 1; i <= data->block[0]; i++)
-				msg[0].buf[i] = data->block[i];
+			memcpy(msg[0].buf + 1, data->block + 1, data->block[0]);
 		}
 		break;
 	default:
@@ -489,13 +486,11 @@  static s32 i2c_smbus_xfer_emulated(struct i2c_adapter *adapter, u16 addr,
 			data->word = get_unaligned_le16(msgbuf1);
 			break;
 		case I2C_SMBUS_I2C_BLOCK_DATA:
-			for (i = 0; i < data->block[0]; i++)
-				data->block[i + 1] = msg[1].buf[i];
+			memcpy(data->block + 1, msg[1].buf, data->block[0]);
 			break;
 		case I2C_SMBUS_BLOCK_DATA:
 		case I2C_SMBUS_BLOCK_PROC_CALL:
-			for (i = 0; i < msg[1].buf[0] + 1; i++)
-				data->block[i] = msg[1].buf[i];
+			memcpy(data->block, msg[1].buf, msg[1].buf[0] + 1);
 			break;
 		}