Re: [Linaro-acpi] [RFC] ACPI: Add new function to get table entries

[Tomasz Nowicki <tomasz.nowicki@linaro.org>]

On 20.03.2014 00:09, Ashwin Chaugule wrote:
> The acpi_table_parse() function has a callback that
> passes a pointer to a table_header. Add a new function
> which takes this pointer and parses its entries. This
> eliminates the need to re-traverse all the tables for
> each call. e.g. as in acpi_table_parse_madt() which is
> normally called after acpi_table_parse().
>
> Signed-off-by: Ashwin Chaugule <ashwin.chaugule@linaro.org>
> ---
>   drivers/acpi/tables.c | 69 +++++++++++++++++++++++++++++++++++----------------
>   include/linux/acpi.h  |  4 +++
>   2 files changed, 51 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/acpi/tables.c b/drivers/acpi/tables.c
> index 5837f85..b7bd6a3 100644
> --- a/drivers/acpi/tables.c
> +++ b/drivers/acpi/tables.c
> @@ -199,19 +199,15 @@ void acpi_table_print_madt_entry(struct acpi_subtable_header *header)
>   	}
>   }
>
> -
>   int __init
> -acpi_table_parse_entries(char *id,
> -			     unsigned long table_size,
> -			     int entry_id,
> -			     acpi_tbl_entry_handler handler,
> -			     unsigned int max_entries)
> +acpi_parse_entries(unsigned long table_size,
> +		acpi_tbl_entry_handler handler,
> +		struct acpi_table_header *table_header,
> +		int entry_id, unsigned int max_entries)
>   {
> -	struct acpi_table_header *table_header = NULL;
>   	struct acpi_subtable_header *entry;
>   	unsigned int count = 0;
>   	unsigned long table_end;
> -	acpi_size tbl_size;
>
>   	if (acpi_disabled)
>   		return -ENODEV;
> @@ -219,16 +215,14 @@ acpi_table_parse_entries(char *id,
>   	if (!handler)
>   		return -EINVAL;
>
> -	if (strncmp(id, ACPI_SIG_MADT, 4) == 0)
> -		acpi_get_table_with_size(id, acpi_apic_instance, &table_header, &tbl_size);
> -	else
> -		acpi_get_table_with_size(id, 0, &table_header, &tbl_size);
> -
>   	if (!table_header) {
> -		printk(KERN_WARNING PREFIX "%4.4s not present\n", id);
> +		pr_warn(PREFIX "Table header not present\n");
>   		return -ENODEV;
>   	}
>
> +	if (!table_size)
> +		table_size = table_header->length;
> +

If table_size == 0, that would causes 'entry' and 'table_end' are equal 
and no entries at all. For that case I would suggest to print error and 
return.

Tomasz

>   	table_end = (unsigned long)table_header + table_header->length;
>
>   	/* Parse all entries looking for a match. */
> @@ -240,15 +234,18 @@ acpi_table_parse_entries(char *id,
>   	       table_end) {
>   		if (entry->type == entry_id
>   		    && (!max_entries || count++ < max_entries))
> -			if (handler(entry, table_end))
> +			if (handler(entry, table_end)) {
> +				count = -EINVAL;
>   				goto err;
> +			}
>
>   		/*
>   		 * If entry->length is 0, break from this loop to avoid
>   		 * infinite loop.
>   		 */
>   		if (entry->length == 0) {
> -			pr_err(PREFIX "[%4.4s:0x%02x] Invalid zero length\n", id, entry_id);
> +			pr_err(PREFIX "[0x%02x] Invalid zero length\n", entry_id);
> +			count = -EINVAL;
>   			goto err;
>   		}
>
> @@ -256,15 +253,43 @@ acpi_table_parse_entries(char *id,
>   		    ((unsigned long)entry + entry->length);
>   	}
>   	if (max_entries && count > max_entries) {
> -		printk(KERN_WARNING PREFIX "[%4.4s:0x%02x] ignored %i entries of "
> -		       "%i found\n", id, entry_id, count - max_entries, count);
> +		printk(KERN_WARNING PREFIX "[0x%02x] ignored %i entries of "
> +		       "%i found\n", entry_id, count - max_entries, count);
>   	}
>
> -	early_acpi_os_unmap_memory((char *)table_header, tbl_size);
> -	return count;
>   err:
> -	early_acpi_os_unmap_memory((char *)table_header, tbl_size);
> -	return -EINVAL;
> +	early_acpi_os_unmap_memory((char *)table_header, (acpi_size)table_size);
> +	return count;

Changelog is saying that acpi_parse_entries() takes already mapped table 
and parses entries. IMO, caller should takes care about unmapping table. 
It can be still parsed using different ID later on.

Tomasz

> +}
> +
> +int __init
> +acpi_table_parse_entries(char *id,
> +			     unsigned long table_size,
> +			     int entry_id,
> +			     acpi_tbl_entry_handler handler,
> +			     unsigned int max_entries)
> +{
> +	struct acpi_table_header *table_header = NULL;
> +	acpi_size tbl_size;
> +
> +	if (acpi_disabled)
> +		return -ENODEV;
> +
> +	if (!handler)
> +		return -EINVAL;
> +
> +	if (strncmp(id, ACPI_SIG_MADT, 4) == 0)
> +		acpi_get_table_with_size(id, acpi_apic_instance, &table_header, &tbl_size);
> +	else
> +		acpi_get_table_with_size(id, 0, &table_header, &tbl_size);
> +
> +	if (!table_header) {
> +		pr_warn("%4.4s not present\n", id);
> +		return -ENODEV;
> +	}
> +
> +	return acpi_parse_entries(table_header->length, handler, table_header,
> +			entry_id, max_entries);
>   }
>
>   int __init
> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> index 1151a1d..da959fd 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -118,6 +118,10 @@ int acpi_numa_init (void);
>
>   int acpi_table_init (void);
>   int acpi_table_parse(char *id, acpi_tbl_table_handler handler);
> +int __init acpi_parse_entries(unsigned long table_size,
> +		acpi_tbl_entry_handler handler,
> +		struct acpi_table_header *table_header,
> +		int entry_id, unsigned int max_entries);
>   int __init acpi_table_parse_entries(char *id, unsigned long table_size,
>   				    int entry_id,
>   				    acpi_tbl_entry_handler handler,
>