linux-kernel - RE: [Linux-fbdev-devel] [PATCH] added S6E63M0 AMOLED LCD Panel driver.

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Date:	Tue, 30 Mar 2010 18:24:51 -0500
From:	H Hartley Sweeten <hartleys@...ionengravers.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	InKi Dae <daeinki@...il.com>
CC:	"kyungmin.park@...sung.com" <kyungmin.park@...sung.com>,
	"linux-fbdev-devel@...ts.sourceforge.net" 
	<linux-fbdev-devel@...ts.sourceforge.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Pavel Machek <pavel@....cz>
Subject: RE: [Linux-fbdev-devel] [PATCH] added S6E63M0 AMOLED LCD Panel
	driver.

On Tuesday, March 30, 2010 4:03 PM, Andrew Morton wrote:
> On Fri, 26 Mar 2010 12:24:24 +0900
> InKi Dae <daeinki@...il.com> wrote:
> 
>> +static int s6e63m0_ldi_init(struct s6e63m0 *lcd)
>> +{
>> +	int ret;
>> +
>> +	ret = s6e63m0_panel_send_sequence(lcd, SEQ_PANEL_CONDITION_SET);
>> +	ret |= s6e63m0_panel_send_sequence(lcd, SEQ_DISPLAY_CONDITION_SET);
>> +	ret |= s6e63m0_panel_send_sequence(lcd, SEQ_GAMMA_SETTING);
>> +	ret |= s6e63m0_panel_send_sequence(lcd, SEQ_ETC_CONDITION_SET);
>> +	ret |= s6e63m0_panel_send_sequence(lcd, SEQ_ACL_ON);
>> +	ret |= s6e63m0_panel_send_sequence(lcd, SEQ_ELVSS_ON);
>> +
>> +	return ret;
>> +}
>
> Well.  If one call to s6e63m0_panel_send_sequence() returns -ENOMEM and
> another call returns -EIO (for example), this function will return some
> other, incorrect errno.
>
> Which is a rather minor problem, unless some caller is explicitly
> looking for some particular error code, which doesn't happen often.

Why not handle the calls with a loop?

+static int s6e63m0_ldi_init(struct s6e63m0 *lcd)
+{
+	const unsigned short *init_seq[] = {
+		SEQ_PANEL_CONDITION_SET,
+		SEQ_DISPLAY_CONDITION_SET,
+		SEQ_GAMMA_SETTING,
+		SEQ_ETC_CONDITION_SET,
+		SEQ_ACL_ON,
+		SEQ_ELVSS_ON,
+	};
+	int i, ret;
+
+	for (i = 0; i < ARRAY_SIZE(init_seq); i++) {
+		ret = s6e63m0_panel_send_sequence(lcd, init_seq[i]);
+		if (ret)
+			break;
+	}
+	return ret;
+}

Note that _s6e63m0_gamma_ctl has the same issue.  Actually, the whole
driver has issues with returning errors properly.

Regards,
Hartley--
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