2017-03-29 07:42:13

by Dmitry Torokhov

Subject: [PATCH] auxdisplay: ht16k33: use le16_to_cpup() to fetch LE16 data

The data read from the device is 3 little-endian words, so let's annotate
them as such and use le16_to_cpu() to convert them to host endianness - it
might turn out to be a bit more performant, and it expresses the conversion
more clearly.

Signed-off-by: Dmitry Torokhov <[email protected]>
---
drivers/auxdisplay/ht16k33.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/auxdisplay/ht16k33.c b/drivers/auxdisplay/ht16k33.c
index f66b45b235b0..61af52a7afd5 100644
--- a/drivers/auxdisplay/ht16k33.c
+++ b/drivers/auxdisplay/ht16k33.c
@@ -254,18 +254,19 @@ static bool ht16k33_keypad_scan(struct ht16k33_keypad *keypad)
{
const unsigned short *keycodes = keypad->dev->keycode;
u16 new_state[HT16K33_MATRIX_KEYPAD_MAX_COLS];
- u8 data[HT16K33_MATRIX_KEYPAD_MAX_COLS * 2];
+ __le16 data[HT16K33_MATRIX_KEYPAD_MAX_COLS];
unsigned long bits_changed;
int row, col, code;
bool pressed = false;

- if (i2c_smbus_read_i2c_block_data(keypad->client, 0x40, 6, data) != 6) {
+ if (i2c_smbus_read_i2c_block_data(keypad->client, 0x40,
+ sizeof(data), (u8 *)data) != 6) {
dev_err(&keypad->client->dev, "Failed to read key data\n");
return false;
}

for (col = 0; col < keypad->cols; col++) {
- new_state[col] = (data[col * 2 + 1] << 8) | data[col * 2];
+ new_state[col] = le16_to_cpu(data[col]);
if (new_state[col])
pressed = true;
bits_changed = keypad->last_key_state[col] ^ new_state[col];
--
2.12.2.564.g063fe858b8-goog


--
Dmitry

2017-03-29 08:14:19

by Robin van der Gracht

Subject: Re: [PATCH] auxdisplay: ht16k33: use le16_to_cpup() to fetch LE16 data

On Wed, 29 Mar 2017 00:42:08 -0700
Dmitry Torokhov <[email protected]> wrote:

> The data read from the device is 3 little-endian words, so let's annotate
> them as such and use le16_to_cpu() to convert them to host endianness - it
> might turn out to be a bit more performant, and it expresses the conversion
> more clearly.

Agreed

>
> Signed-off-by: Dmitry Torokhov <[email protected]>
> ---
> drivers/auxdisplay/ht16k33.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/auxdisplay/ht16k33.c b/drivers/auxdisplay/ht16k33.c
> index f66b45b235b0..61af52a7afd5 100644
> --- a/drivers/auxdisplay/ht16k33.c
> +++ b/drivers/auxdisplay/ht16k33.c
> @@ -254,18 +254,19 @@ static bool ht16k33_keypad_scan(struct ht16k33_keypad *keypad)
> {
> const unsigned short *keycodes = keypad->dev->keycode;
> u16 new_state[HT16K33_MATRIX_KEYPAD_MAX_COLS];
> - u8 data[HT16K33_MATRIX_KEYPAD_MAX_COLS * 2];
> + __le16 data[HT16K33_MATRIX_KEYPAD_MAX_COLS];
> unsigned long bits_changed;
> int row, col, code;
> bool pressed = false;
>
> - if (i2c_smbus_read_i2c_block_data(keypad->client, 0x40, 6, data) != 6) {
> + if (i2c_smbus_read_i2c_block_data(keypad->client, 0x40,
> + sizeof(data), (u8 *)data) != 6) {

Why use sizeof(data) for length but check against the hardcoded 6?

> dev_err(&keypad->client->dev, "Failed to read key data\n");
> return false;
> }
>
> for (col = 0; col < keypad->cols; col++) {
> - new_state[col] = (data[col * 2 + 1] << 8) | data[col * 2];
> + new_state[col] = le16_to_cpu(data[col]);

nice!

> if (new_state[col])
> pressed = true;
> bits_changed = keypad->last_key_state[col] ^ new_state[col];

Robin

2017-04-01 17:24:33

by Dmitry Torokhov

Subject: Re: [PATCH] auxdisplay: ht16k33: use le16_to_cpup() to fetch LE16 data

On Wed, Mar 29, 2017 at 10:13:59AM +0200, Robin van der Gracht wrote:
> On Wed, 29 Mar 2017 00:42:08 -0700
> Dmitry Torokhov <[email protected]> wrote:
>
> > The data read from the device is 3 little-endian words, so let's annotate
> > them as such and use le16_to_cpu() to convert them to host endianness - it
> > might turn out to be a bit more performant, and it expresses the conversion
> > more clearly.
>
> Agreed
>
> >
> > Signed-off-by: Dmitry Torokhov <[email protected]>
> > ---
> > drivers/auxdisplay/ht16k33.c | 7 ++++---
> > 1 file changed, 4 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/auxdisplay/ht16k33.c b/drivers/auxdisplay/ht16k33.c
> > index f66b45b235b0..61af52a7afd5 100644
> > --- a/drivers/auxdisplay/ht16k33.c
> > +++ b/drivers/auxdisplay/ht16k33.c
> > @@ -254,18 +254,19 @@ static bool ht16k33_keypad_scan(struct ht16k33_keypad *keypad)
> > {
> > const unsigned short *keycodes = keypad->dev->keycode;
> > u16 new_state[HT16K33_MATRIX_KEYPAD_MAX_COLS];
> > - u8 data[HT16K33_MATRIX_KEYPAD_MAX_COLS * 2];
> > + __le16 data[HT16K33_MATRIX_KEYPAD_MAX_COLS];
> > unsigned long bits_changed;
> > int row, col, code;
> > bool pressed = false;
> >
> > - if (i2c_smbus_read_i2c_block_data(keypad->client, 0x40, 6, data) != 6) {
> > + if (i2c_smbus_read_i2c_block_data(keypad->client, 0x40,
> > + sizeof(data), (u8 *)data) != 6) {
>
> Why use sizeof(data) for length but check against the hardcoded 6?

It was quite late into the night ;) V2 is coming.

>
> > dev_err(&keypad->client->dev, "Failed to read key data\n");
> > return false;
> > }
> >
> > for (col = 0; col < keypad->cols; col++) {
> > - new_state[col] = (data[col * 2 + 1] << 8) | data[col * 2];
> > + new_state[col] = le16_to_cpu(data[col]);
>
> nice!
>
> > if (new_state[col])
> > pressed = true;
> > bits_changed = keypad->last_key_state[col] ^ new_state[col];
>
> Robin

--
Dmitry