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* [PATCH] staging: panel: change struct bits to a bit array
@ 2015-03-13 16:42 Isaac Lleida
  2015-03-16  9:08 ` Dan Carpenter
  0 siblings, 1 reply; 2+ messages in thread
From: Isaac Lleida @ 2015-03-13 16:42 UTC (permalink / raw)
  To: willy
  Cc: gregkh, marius.gorski, armand.bastien, domdevlin,
	sudipm.mukherjee, devel, linux-kernel, isaky

From: isaky <illeida@openaliasbox.org>

This path implements a bit array representing the LCD signal states instead of the old "struct bits", which used char to represent a single bit. This will reduce the memory usage.

Signed-off-by: Isaac Lleida <illeida@openaliasbox.org>
---
 drivers/staging/panel/panel.c | 86 ++++++++++++++++++++++++-------------------
 1 file changed, 49 insertions(+), 37 deletions(-)

diff --git a/drivers/staging/panel/panel.c b/drivers/staging/panel/panel.c
index 3339633..7deb092 100644
--- a/drivers/staging/panel/panel.c
+++ b/drivers/staging/panel/panel.c
@@ -310,6 +310,25 @@ static int selected_lcd_type = NOT_SET;
 #define LCD_BITS	6
 
 /*
+ * LCD signal states
+ */
+#define LCD_BIT_E_MASK		0x1	/* E (data latch on falling edge) */
+#define LCD_BIT_RS_MASK		0x2	/* RS  (0 = cmd, 1 = data) */
+#define LCD_BIT_RW_MASK		0x4	/* R/W (0 = W, 1 = R) */
+#define LCD_BIT_BL_MASK		0x8	/* backlight (0 = off, 1 = on) */
+#define LCD_BIT_CL_MASK		0x10	/* clock (latch on rising edge) */
+#define LCD_BIT_DA_MASK		0x20	/* data */
+
+/*
+ * Bit array operations
+ */
+#define BIT_ON(b, m)	(b |= m)
+#define BIT_OFF(b, m)	(b &= ~m)
+#define BIT_CHK(b, m)	(b & m)
+#define BIT_MOD(b, m, v)			\
+	((v) ? BIT_ON(b, m) : BIT_OFF(b, m))	\
+
+/*
  * each bit can be either connected to a DATA or CTRL port
  */
 #define LCD_PORT_C	0
@@ -653,15 +672,8 @@ static const char nexcom_keypad_profile[][4][9] = {
 
 static const char (*keypad_profile)[4][9] = old_keypad_profile;
 
-/* FIXME: this should be converted to a bit array containing signals states */
-static struct {
-	unsigned char e;  /* parallel LCD E (data latch on falling edge) */
-	unsigned char rs; /* parallel LCD RS  (0 = cmd, 1 = data) */
-	unsigned char rw; /* parallel LCD R/W (0 = W, 1 = R) */
-	unsigned char bl; /* parallel LCD backlight (0 = off, 1 = on) */
-	unsigned char cl; /* serial LCD clock (latch on rising edge) */
-	unsigned char da; /* serial LCD data */
-} bits;
+/* Bit array containing signals states */
+static char bits;
 
 static void init_scan_timer(void);
 
@@ -674,12 +686,12 @@ static int set_data_bits(void)
 	for (bit = 0; bit < LCD_BITS; bit++)
 		val &= lcd_bits[LCD_PORT_D][bit][BIT_MSK];
 
-	val |= lcd_bits[LCD_PORT_D][LCD_BIT_E][bits.e]
-	    | lcd_bits[LCD_PORT_D][LCD_BIT_RS][bits.rs]
-	    | lcd_bits[LCD_PORT_D][LCD_BIT_RW][bits.rw]
-	    | lcd_bits[LCD_PORT_D][LCD_BIT_BL][bits.bl]
-	    | lcd_bits[LCD_PORT_D][LCD_BIT_CL][bits.cl]
-	    | lcd_bits[LCD_PORT_D][LCD_BIT_DA][bits.da];
+	val |= lcd_bits[LCD_PORT_D][LCD_BIT_E][BIT_CHK(bits, LCD_BIT_E_MASK)]
+	    | lcd_bits[LCD_PORT_D][LCD_BIT_RS][BIT_CHK(bits, LCD_BIT_RS_MASK)]
+	    | lcd_bits[LCD_PORT_D][LCD_BIT_RW][BIT_CHK(bits, LCD_BIT_RW_MASK)]
+	    | lcd_bits[LCD_PORT_D][LCD_BIT_BL][BIT_CHK(bits, LCD_BIT_BL_MASK)]
+	    | lcd_bits[LCD_PORT_D][LCD_BIT_CL][BIT_CHK(bits, LCD_BIT_CL_MASK)]
+	    | lcd_bits[LCD_PORT_D][LCD_BIT_DA][BIT_CHK(bits, LCD_BIT_DA_MASK)];
 
 	w_dtr(pprt, val);
 	return val;
@@ -694,12 +706,12 @@ static int set_ctrl_bits(void)
 	for (bit = 0; bit < LCD_BITS; bit++)
 		val &= lcd_bits[LCD_PORT_C][bit][BIT_MSK];
 
-	val |= lcd_bits[LCD_PORT_C][LCD_BIT_E][bits.e]
-	    | lcd_bits[LCD_PORT_C][LCD_BIT_RS][bits.rs]
-	    | lcd_bits[LCD_PORT_C][LCD_BIT_RW][bits.rw]
-	    | lcd_bits[LCD_PORT_C][LCD_BIT_BL][bits.bl]
-	    | lcd_bits[LCD_PORT_C][LCD_BIT_CL][bits.cl]
-	    | lcd_bits[LCD_PORT_C][LCD_BIT_DA][bits.da];
+	val |= lcd_bits[LCD_PORT_C][LCD_BIT_E][BIT_CHK(bits, LCD_BIT_E_MASK)]
+	    | lcd_bits[LCD_PORT_C][LCD_BIT_RS][BIT_CHK(bits, LCD_BIT_RS_MASK)]
+	    | lcd_bits[LCD_PORT_C][LCD_BIT_RW][BIT_CHK(bits, LCD_BIT_RW_MASK)]
+	    | lcd_bits[LCD_PORT_C][LCD_BIT_BL][BIT_CHK(bits, LCD_BIT_BL_MASK)]
+	    | lcd_bits[LCD_PORT_C][LCD_BIT_CL][BIT_CHK(bits, LCD_BIT_BL_MASK)]
+	    | lcd_bits[LCD_PORT_C][LCD_BIT_DA][BIT_CHK(bits, LCD_BIT_DA_MASK)];
 
 	w_ctr(pprt, val);
 	return val;
@@ -794,12 +806,12 @@ static void lcd_send_serial(int byte)
 	/* the data bit is set on D0, and the clock on STROBE.
 	 * LCD reads D0 on STROBE's rising edge. */
 	for (bit = 0; bit < 8; bit++) {
-		bits.cl = BIT_CLR;	/* CLK low */
+		BIT_OFF(bits, LCD_BIT_CL_MASK);	/* CLK low */
 		panel_set_bits();
-		bits.da = byte & 1;
+		BIT_MOD(bits, LCD_BIT_DA_MASK, byte & 1);
 		panel_set_bits();
 		udelay(2);  /* maintain the data during 2 us before CLK up */
-		bits.cl = BIT_SET;	/* CLK high */
+		BIT_ON(bits, LCD_BIT_CL_MASK);	/* CLK high */
 		panel_set_bits();
 		udelay(1);  /* maintain the strobe during 1 us */
 		byte >>= 1;
@@ -814,7 +826,7 @@ static void lcd_backlight(int on)
 
 	/* The backlight is activated by setting the AUTOFEED line to +5V  */
 	spin_lock_irq(&pprt_lock);
-	bits.bl = on;
+	BIT_MOD(bits, LCD_BIT_BL_MASK, on);
 	panel_set_bits();
 	spin_unlock_irq(&pprt_lock);
 }
@@ -849,14 +861,14 @@ static void lcd_write_cmd_p8(int cmd)
 	w_dtr(pprt, cmd);
 	udelay(20);	/* maintain the data during 20 us before the strobe */
 
-	bits.e = BIT_SET;
-	bits.rs = BIT_CLR;
-	bits.rw = BIT_CLR;
+	BIT_ON(bits, LCD_BIT_E_MASK);
+	BIT_OFF(bits, LCD_BIT_RS_MASK);
+	BIT_OFF(bits, LCD_BIT_RW_MASK);
 	set_ctrl_bits();
 
 	udelay(40);	/* maintain the strobe during 40 us */
 
-	bits.e = BIT_CLR;
+	BIT_OFF(bits, LCD_BIT_E_MASK);
 	set_ctrl_bits();
 
 	udelay(120);	/* the shortest command takes at least 120 us */
@@ -871,14 +883,14 @@ static void lcd_write_data_p8(int data)
 	w_dtr(pprt, data);
 	udelay(20);	/* maintain the data during 20 us before the strobe */
 
-	bits.e = BIT_SET;
-	bits.rs = BIT_SET;
-	bits.rw = BIT_CLR;
+	BIT_ON(bits, LCD_BIT_E_MASK);
+	BIT_OFF(bits, LCD_BIT_RS_MASK);
+	BIT_OFF(bits, LCD_BIT_RW_MASK);
 	set_ctrl_bits();
 
 	udelay(40);	/* maintain the strobe during 40 us */
 
-	bits.e = BIT_CLR;
+	BIT_OFF(bits, LCD_BIT_E_MASK);
 	set_ctrl_bits();
 
 	udelay(45);	/* the shortest data takes at least 45 us */
@@ -968,15 +980,15 @@ static void lcd_clear_fast_p8(void)
 		/* maintain the data during 20 us before the strobe */
 		udelay(20);
 
-		bits.e = BIT_SET;
-		bits.rs = BIT_SET;
-		bits.rw = BIT_CLR;
+		BIT_ON(bits, LCD_BIT_E_MASK);
+		BIT_OFF(bits, LCD_BIT_RS_MASK);
+		BIT_OFF(bits, LCD_BIT_RW_MASK);
 		set_ctrl_bits();
 
 		/* maintain the strobe during 40 us */
 		udelay(40);
 
-		bits.e = BIT_CLR;
+		BIT_OFF(bits, LCD_BIT_E_MASK);
 		set_ctrl_bits();
 
 		/* the shortest data takes at least 45 us */
-- 
2.3.2


^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: [PATCH] staging: panel: change struct bits to a bit array
  2015-03-13 16:42 [PATCH] staging: panel: change struct bits to a bit array Isaac Lleida
@ 2015-03-16  9:08 ` Dan Carpenter
  0 siblings, 0 replies; 2+ messages in thread
From: Dan Carpenter @ 2015-03-16  9:08 UTC (permalink / raw)
  To: Isaac Lleida
  Cc: willy, devel, isaky, armand.bastien, gregkh, linux-kernel,
	marius.gorski, domdevlin, sudipm.mukherjee

On Fri, Mar 13, 2015 at 05:42:03PM +0100, Isaac Lleida wrote:
> From: isaky <illeida@openaliasbox.org>

Not your name.  Leave this out unless you are passing on someone else's
patch.

> 
> This path implements a bit array representing the LCD signal states instead of the old "struct bits", which used char to represent a single bit. This will reduce the memory usage.
> 

Line wraps the changelog.

> Signed-off-by: Isaac Lleida <illeida@openaliasbox.org>

This should match the email address you used to send the patch.


> ---
>  drivers/staging/panel/panel.c | 86 ++++++++++++++++++++++++-------------------
>  1 file changed, 49 insertions(+), 37 deletions(-)
> 
> diff --git a/drivers/staging/panel/panel.c b/drivers/staging/panel/panel.c
> index 3339633..7deb092 100644
> --- a/drivers/staging/panel/panel.c
> +++ b/drivers/staging/panel/panel.c
> @@ -310,6 +310,25 @@ static int selected_lcd_type = NOT_SET;
>  #define LCD_BITS	6
>  
>  /*
> + * LCD signal states
> + */
> +#define LCD_BIT_E_MASK		0x1	/* E (data latch on falling edge) */
> +#define LCD_BIT_RS_MASK		0x2	/* RS  (0 = cmd, 1 = data) */
> +#define LCD_BIT_RW_MASK		0x4	/* R/W (0 = W, 1 = R) */
> +#define LCD_BIT_BL_MASK		0x8	/* backlight (0 = off, 1 = on) */
> +#define LCD_BIT_CL_MASK		0x10	/* clock (latch on rising edge) */
> +#define LCD_BIT_DA_MASK		0x20	/* data */
> +
> +/*
> + * Bit array operations
> + */
> +#define BIT_ON(b, m)	(b |= m)
> +#define BIT_OFF(b, m)	(b &= ~m)
> +#define BIT_CHK(b, m)	(b & m)
> +#define BIT_MOD(b, m, v)			\
> +	((v) ? BIT_ON(b, m) : BIT_OFF(b, m))	\
> +


Ugh.  No.  These are yuck macros.  Just do it directly.  Also the
BIT_MOD() has end in a '\' char.

> +/*
>   * each bit can be either connected to a DATA or CTRL port
>   */
>  #define LCD_PORT_C	0
> @@ -653,15 +672,8 @@ static const char nexcom_keypad_profile[][4][9] = {
>  
>  static const char (*keypad_profile)[4][9] = old_keypad_profile;
>  
> -/* FIXME: this should be converted to a bit array containing signals states */
> -static struct {
> -	unsigned char e;  /* parallel LCD E (data latch on falling edge) */
> -	unsigned char rs; /* parallel LCD RS  (0 = cmd, 1 = data) */
> -	unsigned char rw; /* parallel LCD R/W (0 = W, 1 = R) */
> -	unsigned char bl; /* parallel LCD backlight (0 = off, 1 = on) */
> -	unsigned char cl; /* serial LCD clock (latch on rising edge) */
> -	unsigned char da; /* serial LCD data */
> -} bits;
> +/* Bit array containing signals states */
> +static char bits;

I don't think this is what the comment means.  I think it means that
we do something like:

static struct {
	unsigned long e:1;
	unsigned long rs:1;
	...
} bits;

1) This space saving are very small.  On 64 bit systems then we don't
save any space at all because everything is aligned at 8 bytes.
2) The name "e" is not self documenting.  None of them are.

Christophe had a bunch more comments on this patch so I'm not going to
read any further.

regards,
dan carpenter


^ permalink raw reply	[flat|nested] 2+ messages in thread

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