linux-kernel - Re: [Patch v2 3/3] firmware: dmi_scan: use direct access to static vars

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Date:	Mon, 13 Apr 2015 19:26:23 +0200
From:	Jean Delvare <jdelvare@...e.de>
To:	Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
Cc:	matt.fleming@...el.com, ard.biesheuvel@...aro.org,
	leif.lindholm@...aro.org, linux-kernel@...r.kernel.org
Subject: Re: [Patch v2 3/3] firmware: dmi_scan: use direct access to static
 vars

On Wed, 18 Feb 2015 13:33:21 +0200, Ivan Khoronzhuk wrote:
> There is no reason to pass static vars to function that can use
> only them.
> 
> The dmi_table() can use only dmi_len and dmi_num static vars, so use
> them directly. In this case we can freely change their type in one
> place and slightly decrease redundancy.

Too bad we changed dmi_len's type already ;-)

I can see the benefit, and even if this certainly makes dmi_table
slightly slower, no objection from me.

> Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@...aro.org>
> ---
>  drivers/firmware/dmi_scan.c | 17 +++++++++--------
>  1 file changed, 9 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/firmware/dmi_scan.c b/drivers/firmware/dmi_scan.c
> index 3f3470f..8c065f7 100644
> --- a/drivers/firmware/dmi_scan.c
> +++ b/drivers/firmware/dmi_scan.c
> @@ -18,6 +18,8 @@
>  static const char dmi_empty_string[] = "        ";
>  
>  static u32 dmi_ver __initdata;
> +static u32 dmi_len;
> +static u16 dmi_num;

A blank line here wouldn't hurt.

>  /*
>   * Catch too early calls to dmi_check_system():
>   */
> @@ -78,7 +80,7 @@ static const char * __init dmi_string(const struct dmi_header *dm, u8 s)
>   *	We have to be cautious here. We have seen BIOSes with DMI pointers
>   *	pointing to completely the wrong place for example
>   */
> -static void dmi_table(u8 *buf, u32 len, int num,
> +static void dmi_table(u8 *buf,
>  		      void (*decode)(const struct dmi_header *, void *),
>  		      void *private_data)
>  {
> @@ -89,7 +91,8 @@ static void dmi_table(u8 *buf, u32 len, int num,
>  	 *	Stop when we see all the items the table claimed to have
>  	 *	OR we run off the end of the table (also happens)
>  	 */
> -	while ((i < num) && (data - buf + sizeof(struct dmi_header)) <= len) {
> +	while ((i < dmi_num) && (data - buf + sizeof(struct dmi_header))
> +		<= dmi_len) {

One condition per line is easier to read:

	while ((i < dmi_num) &&
	       (data - buf + sizeof(struct dmi_header)) <= dmi_len) {

>  		const struct dmi_header *dm = (const struct dmi_header *)data;
>  
>  		/*
> @@ -98,9 +101,9 @@ static void dmi_table(u8 *buf, u32 len, int num,
>  		 *  table in dmi_decode or dmi_string
>  		 */
>  		data += dm->length;
> -		while ((data - buf < len - 1) && (data[0] || data[1]))
> +		while ((data - buf < dmi_len - 1) && (data[0] || data[1]))
>  			data++;
> -		if (data - buf < len - 1)
> +		if (data - buf < dmi_len - 1)
>  			decode(dm, private_data);
>  
>  		/*
> @@ -117,8 +120,6 @@ static void dmi_table(u8 *buf, u32 len, int num,
>  static u8 smbios_header[32];
>  static int smbios_header_size;
>  static phys_addr_t dmi_base;
> -static u32 dmi_len;
> -static u16 dmi_num;
>  
>  static int __init dmi_walk_early(void (*decode)(const struct dmi_header *,
>  		void *))
> @@ -129,7 +130,7 @@ static int __init dmi_walk_early(void (*decode)(const struct dmi_header *,
>  	if (buf == NULL)
>  		return -1;
>  
> -	dmi_table(buf, dmi_len, dmi_num, decode, NULL);
> +	dmi_table(buf, decode, NULL);
>  
>  	add_device_randomness(buf, dmi_len);
>  
> @@ -913,7 +914,7 @@ int dmi_walk(void (*decode)(const struct dmi_header *, void *),
>  	if (buf == NULL)
>  		return -1;
>  
> -	dmi_table(buf, dmi_len, dmi_num, decode, private_data);
> +	dmi_table(buf, decode, private_data);
>  
>  	dmi_unmap(buf);
>  	return 0;

-- 
Jean Delvare
SUSE L3 Support
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