RE: [PATCH 1/2] acpi,backlight: MSI S270 laptop support - ec_transaction()

["Yu, Luming" <luming.yu@intel.com>]

First of all, thanks for your patch.
 
>+static int acpi_ec_transaction(union acpi_ec *ec, u8 command,
>+                               const u8 *wdata, unsigned wdata_len,
>+                               u8 *rdata, unsigned rdata_len)

I agree the name: transaction sounds better than read/write, and
can reduce redundant code from separate read, write function.
But, I guess using argument : u8 address will make the patch
looks better.

>+{
>+        if (acpi_ec_poll_mode)
>+                return acpi_ec_poll_transaction(ec, command, 
>wdata, wdata_len, rdata, rdata_len);
>+        else
>+                return acpi_ec_intr_transaction(ec, command, 
>wdata, wdata_len, rdata, rdata_len);
>+}
>+

It would be better to use a function pointer instead of
using if-lese statement which looks not so neat.

> static int acpi_ec_read(union acpi_ec *ec, u8 address, u32 * data)
> {
>-	if (acpi_ec_poll_mode)
>-		return acpi_ec_poll_read(ec, address, data);
>-	else
>-		return acpi_ec_intr_read(ec, address, data);
>+        int result;
>+        u8 d;
>+        result = acpi_ec_transaction(ec, 
>ACPI_EC_COMMAND_READ, &address, 1, &d, 1);
>+        *data = d;
>+        return result;
> }

Due to missing argument: address, you have to pass address in
argument: wdata. This kind of code style is prone to error.


> static int acpi_ec_write(union acpi_ec *ec, u8 address, u8 data)
> {
>-	if (acpi_ec_poll_mode)
>-		return acpi_ec_poll_write(ec, address, data);
>-	else
>-		return acpi_ec_intr_write(ec, address, data);
>+        u8 wdata[2] = { address, data };
>+        return acpi_ec_transaction(ec, ACPI_EC_COMMAND_WRITE, 
>wdata, 2, NULL, 0);
> }

It would be more clear if there is argument : address.

>-static int acpi_ec_poll_read(union acpi_ec *ec, u8 address, 
>u32 * data)
>+
>+static int acpi_ec_poll_transaction(union acpi_ec *ec, u8 command,
>+                                    const u8 *wdata, unsigned 
>wdata_len,
>+                                    u8 *rdata, unsigned rdata_len)
> {
> 	acpi_status status = AE_OK;
> 	int result = 0;
> 	unsigned long flags = 0;
> 	u32 glk = 0;
> 
>-	ACPI_FUNCTION_TRACE("acpi_ec_read");
>+	ACPI_FUNCTION_TRACE("acpi_ec_poll_transaction");
> 
>-	if (!ec || !data)
>+	if (!ec || !wdata || !wdata_len || (rdata_len && !rdata))
> 		return_VALUE(-EINVAL);


why return -EINVAL if wdata_len == 0?

Thanks
Luming
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