Use bitfield and bitmask macros to clearly specify AD9832 SPI
command fields to make register write code more readable.

Reviewed-by: Marcelo Schmitt <marcelo.schmitt1@gmail.com>
Suggested-by: Marcelo Schmitt <marcelo.schmitt1@gmail.com>
Signed-off-by: Siddharth Menon <simeddon@gmail.com>
---
 v1->v2:
 - remove CMD_SHIFT and ADD_SHIFT
 - use GENMASK
 - store regval in an array and iterate through it
 v2->v3:
 - add missing header
 - refactor code in the previously introduced loops
 v3->v4:
 - update commit message with a better one
 - convert AD9832_PHASE and RES_MASK to masks
 - cleanup a few if else blocks
 v4->v5
 - remove unnecessary inversion (val ? 0 : 1) used
   with AD9832_PHASE_MASK introduced in v4
 - use ARRAY_SIZE instead of fixed integers
 - use reverse xmas tree order
 - align mask macros
 v5->v6
 - rearranged includes to be alphabetical
 - remove unused RES_MASK
 - corrected logical errors pointed out by Marcelo
 v6->v7
 - fix st->ctrl_x alignment
 drivers/staging/iio/frequency/ad9832.c | 92 ++++++++++++++------------
 1 file changed, 48 insertions(+), 44 deletions(-)

diff --git a/drivers/staging/iio/frequency/ad9832.c b/drivers/staging/iio/frequency/ad9832.c
index 140ee4f9c137..08891d66b896 100644
--- a/drivers/staging/iio/frequency/ad9832.c
+++ b/drivers/staging/iio/frequency/ad9832.c
@@ -7,6 +7,8 @@
 
 #include <asm/div64.h>
 
+#include <linux/bitfield.h>
+#include <linux/bits.h>
 #include <linux/clk.h>
 #include <linux/device.h>
 #include <linux/err.h>
@@ -16,6 +18,7 @@
 #include <linux/slab.h>
 #include <linux/spi/spi.h>
 #include <linux/sysfs.h>
+#include <linux/unaligned.h>
 
 #include <linux/iio/iio.h>
 #include <linux/iio/sysfs.h>
@@ -59,17 +62,17 @@
 #define AD9832_CMD_SLEEPRESCLR	0xC
 
 #define AD9832_FREQ		BIT(11)
-#define AD9832_PHASE(x)		(((x) & 3) << 9)
+#define AD9832_PHASE_MASK	GENMASK(10, 9)
 #define AD9832_SYNC		BIT(13)
 #define AD9832_SELSRC		BIT(12)
 #define AD9832_SLEEP		BIT(13)
 #define AD9832_RESET		BIT(12)
 #define AD9832_CLR		BIT(11)
-#define CMD_SHIFT		12
-#define ADD_SHIFT		8
 #define AD9832_FREQ_BITS	32
 #define AD9832_PHASE_BITS	12
-#define RES_MASK(bits)		((1 << (bits)) - 1)
+#define AD9832_CMD_MSK		GENMASK(15, 12)
+#define AD9832_ADD_MSK		GENMASK(11, 8)
+#define AD9832_DAT_MSK		GENMASK(7, 0)
 
 /**
  * struct ad9832_state - driver instance specific data
@@ -131,6 +134,8 @@ static int ad9832_write_frequency(struct ad9832_state *st,
 {
 	unsigned long clk_freq;
 	unsigned long regval;
+	u8 regval_bytes[4];
+	u16 freq_cmd;
 
 	clk_freq = clk_get_rate(st->mclk);
 
@@ -138,19 +143,15 @@ static int ad9832_write_frequency(struct ad9832_state *st,
 		return -EINVAL;
 
 	regval = ad9832_calc_freqreg(clk_freq, fout);
+	put_unaligned_be32(regval, regval_bytes);
 
-	st->freq_data[0] = cpu_to_be16((AD9832_CMD_FRE8BITSW << CMD_SHIFT) |
-					(addr << ADD_SHIFT) |
-					((regval >> 24) & 0xFF));
-	st->freq_data[1] = cpu_to_be16((AD9832_CMD_FRE16BITSW << CMD_SHIFT) |
-					((addr - 1) << ADD_SHIFT) |
-					((regval >> 16) & 0xFF));
-	st->freq_data[2] = cpu_to_be16((AD9832_CMD_FRE8BITSW << CMD_SHIFT) |
-					((addr - 2) << ADD_SHIFT) |
-					((regval >> 8) & 0xFF));
-	st->freq_data[3] = cpu_to_be16((AD9832_CMD_FRE16BITSW << CMD_SHIFT) |
-					((addr - 3) << ADD_SHIFT) |
-					((regval >> 0) & 0xFF));
+	for (int i = 0; i < ARRAY_SIZE(regval_bytes); i++) {
+		freq_cmd = (i % 2 == 0) ? AD9832_CMD_FRE8BITSW : AD9832_CMD_FRE16BITSW;
+
+		st->freq_data[i] = cpu_to_be16(FIELD_PREP(AD9832_CMD_MSK, freq_cmd) |
+			FIELD_PREP(AD9832_ADD_MSK, addr - i) |
+			FIELD_PREP(AD9832_DAT_MSK, regval_bytes[i]));
+	}
 
 	return spi_sync(st->spi, &st->freq_msg);
 }
@@ -158,15 +159,21 @@ static int ad9832_write_frequency(struct ad9832_state *st,
 static int ad9832_write_phase(struct ad9832_state *st,
 			      unsigned long addr, unsigned long phase)
 {
+	u8 phase_bytes[2];
+	u16 phase_cmd;
+
 	if (phase >= BIT(AD9832_PHASE_BITS))
 		return -EINVAL;
 
-	st->phase_data[0] = cpu_to_be16((AD9832_CMD_PHA8BITSW << CMD_SHIFT) |
-					(addr << ADD_SHIFT) |
-					((phase >> 8) & 0xFF));
-	st->phase_data[1] = cpu_to_be16((AD9832_CMD_PHA16BITSW << CMD_SHIFT) |
-					((addr - 1) << ADD_SHIFT) |
-					(phase & 0xFF));
+	put_unaligned_be16(phase, phase_bytes);
+
+	for (int i = 0; i < ARRAY_SIZE(phase_bytes); i++) {
+		phase_cmd = (i % 2 == 0) ? AD9832_CMD_PHA8BITSW : AD9832_CMD_PHA16BITSW;
+
+		st->phase_data[i] = cpu_to_be16(FIELD_PREP(AD9832_CMD_MSK, phase_cmd) |
+			FIELD_PREP(AD9832_ADD_MSK, addr - i) |
+			FIELD_PREP(AD9832_DAT_MSK, phase_bytes[i]));
+	}
 
 	return spi_sync(st->spi, &st->phase_msg);
 }
@@ -197,25 +204,23 @@ static ssize_t ad9832_write(struct device *dev, struct device_attribute *attr,
 		ret = ad9832_write_phase(st, this_attr->address, val);
 		break;
 	case AD9832_PINCTRL_EN:
-		if (val)
-			st->ctrl_ss &= ~AD9832_SELSRC;
-		else
-			st->ctrl_ss |= AD9832_SELSRC;
-		st->data = cpu_to_be16((AD9832_CMD_SYNCSELSRC << CMD_SHIFT) |
-					st->ctrl_ss);
+		st->ctrl_ss &= ~AD9832_SELSRC;
+		st->ctrl_ss |= FIELD_PREP(AD9832_SELSRC, val ? 0 : 1);
+
+		st->data = cpu_to_be16(FIELD_PREP(AD9832_CMD_MSK, AD9832_CMD_SYNCSELSRC) |
+							st->ctrl_ss);
 		ret = spi_sync(st->spi, &st->msg);
 		break;
 	case AD9832_FREQ_SYM:
-		if (val == 1) {
-			st->ctrl_fp |= AD9832_FREQ;
-		} else if (val == 0) {
+		if (val == 1 || val == 0) {
 			st->ctrl_fp &= ~AD9832_FREQ;
+			st->ctrl_fp |= FIELD_PREP(AD9832_FREQ, val ? 1 : 0);
 		} else {
 			ret = -EINVAL;
 			break;
 		}
-		st->data = cpu_to_be16((AD9832_CMD_FPSELECT << CMD_SHIFT) |
-					st->ctrl_fp);
+		st->data = cpu_to_be16(FIELD_PREP(AD9832_CMD_MSK, AD9832_CMD_FPSELECT) |
+							st->ctrl_fp);
 		ret = spi_sync(st->spi, &st->msg);
 		break;
 	case AD9832_PHASE_SYM:
@@ -224,22 +229,21 @@ static ssize_t ad9832_write(struct device *dev, struct device_attribute *attr,
 			break;
 		}
 
-		st->ctrl_fp &= ~AD9832_PHASE(3);
-		st->ctrl_fp |= AD9832_PHASE(val);
+		st->ctrl_fp &= ~AD9832_PHASE_MASK;
+		st->ctrl_fp |= FIELD_PREP(AD9832_PHASE_MASK, val);
 
-		st->data = cpu_to_be16((AD9832_CMD_FPSELECT << CMD_SHIFT) |
-					st->ctrl_fp);
+		st->data = cpu_to_be16(FIELD_PREP(AD9832_CMD_MSK, AD9832_CMD_FPSELECT) |
+							st->ctrl_fp);
 		ret = spi_sync(st->spi, &st->msg);
 		break;
 	case AD9832_OUTPUT_EN:
 		if (val)
-			st->ctrl_src &= ~(AD9832_RESET | AD9832_SLEEP |
-					AD9832_CLR);
+			st->ctrl_src &= ~(AD9832_RESET | AD9832_SLEEP | AD9832_CLR);
 		else
-			st->ctrl_src |= AD9832_RESET;
+			st->ctrl_src |= FIELD_PREP(AD9832_RESET, 1);
 
-		st->data = cpu_to_be16((AD9832_CMD_SLEEPRESCLR << CMD_SHIFT) |
-					st->ctrl_src);
+		st->data = cpu_to_be16(FIELD_PREP(AD9832_CMD_MSK, AD9832_CMD_SLEEPRESCLR) |
+							st->ctrl_src);
 		ret = spi_sync(st->spi, &st->msg);
 		break;
 	default:
@@ -396,8 +400,8 @@ static int ad9832_probe(struct spi_device *spi)
 	spi_message_add_tail(&st->phase_xfer[1], &st->phase_msg);
 
 	st->ctrl_src = AD9832_SLEEP | AD9832_RESET | AD9832_CLR;
-	st->data = cpu_to_be16((AD9832_CMD_SLEEPRESCLR << CMD_SHIFT) |
-					st->ctrl_src);
+	st->data = cpu_to_be16(FIELD_PREP(AD9832_CMD_MSK, AD9832_CMD_SLEEPRESCLR) |
+						st->ctrl_src);
 	ret = spi_sync(st->spi, &st->msg);
 	if (ret) {
 		dev_err(&spi->dev, "device init failed\n");
-- 
2.49.0

On 04/15, Siddharth Menon wrote:
> Use bitfield and bitmask macros to clearly specify AD9832 SPI
> command fields to make register write code more readable.
> 
> Reviewed-by: Marcelo Schmitt <marcelo.schmitt1@gmail.com>
> Suggested-by: Marcelo Schmitt <marcelo.schmitt1@gmail.com>
> Signed-off-by: Siddharth Menon <simeddon@gmail.com>
> ---
...
>  v6->v7
>  - fix st->ctrl_x alignment
>  drivers/staging/iio/frequency/ad9832.c | 92 ++++++++++++++------------
>  1 file changed, 48 insertions(+), 44 deletions(-)
> 
> diff --git a/drivers/staging/iio/frequency/ad9832.c b/drivers/staging/iio/frequency/ad9832.c
...
> -		st->data = cpu_to_be16((AD9832_CMD_SYNCSELSRC << CMD_SHIFT) |
> -					st->ctrl_ss);
> +		st->ctrl_ss &= ~AD9832_SELSRC;
> +		st->ctrl_ss |= FIELD_PREP(AD9832_SELSRC, val ? 0 : 1);
> +
> +		st->data = cpu_to_be16(FIELD_PREP(AD9832_CMD_MSK, AD9832_CMD_SYNCSELSRC) |
> +							st->ctrl_ss);
Oof getting Linux code style compliant tabs and spaces correctly can be tricky.
In sum, tabs should be size 8 and be actual tabs (not 8 blank characters).
Also, when we need to align code at some column that doesn't match 8 sized tabs
exactly, we start with tabs and go until the last tab that precedes the column
we want to align to, then we use spaces to go from that last tab until the
column we want to align to.

For this particular example, the opening parenthesis of FIELD_PREP is at column
50, so to align st->ctrl_ss with the arguments of FIELD_PREP on the preceding
line, we use 6 tabs and 2 spaces.

		st->data = cpu_to_be16(FIELD_PREP(AD9832_CMD_MSK, AD9832_CMD_SYNCSELSRC) |
						  st->ctrl_ss);

Setting tabs the right size depends on the code editor. For vim, the following
settings should ensure the correct tab size.
set tabstop=8
set shiftwidth=8
set softtabstop=0 
set noexpandtab

See Documentation/process/coding-style.rst for complete code style guidance.

Apply the same spacing to the other cases.

Regards,
Marcelo