Re: [PATCH] mtd: cmdlinepart: use cmdline partition parser lib

[Ezequiel Garcia <ezequiel.garcia@free-electrons.com>]

Hi Cai,

Sorry for the late review. See below some minor comments.

On Thu, Aug 15, 2013 at 11:19:36AM +0000, Caizhiyong wrote:
> From: Cai Zhiyong <caizhiyong@huawei.com>
> 
> MTD cmdline partition use cmdline partition parser lib
> 
> reference: https://lkml.org/lkml/2013/8/6/550
> 

How about some more verbose commit message explaining the impact
of this change, or clearly stating there's no functionality change
(as it should given the mtdparts parameter _must_ be kept compatible).

> Signed-off-by: Cai ZhiYong <caizhiyong@huawei.com>
> ---
>  Documentation/block/cmdline-partition.txt |  93 +++++---
>  block/cmdline-parser.c                    |  16 +-
>  drivers/mtd/Kconfig                       |   1 +
>  drivers/mtd/cmdlinepart.c                 | 361 ++++--------------------------
>  include/linux/cmdline-parser.h            |   8 +-
>  5 files changed, 111 insertions(+), 368 deletions(-)
> 

This a nice diffstat, nice job!

> diff --git a/Documentation/block/cmdline-partition.txt b/Documentation/block/cmdline-partition.txt
> index 651863d..adc5f7a 100644
> --- a/Documentation/block/cmdline-partition.txt
> +++ b/Documentation/block/cmdline-partition.txt
> @@ -1,40 +1,59 @@
>  Embedded device command line partition
> -=====================================================================
> -
> -Read block device partition table from command line.
> -The partition used for fixed block device (eMMC) embedded device.
> -It is no MBR, save storage space. Bootloader can be easily accessed
> -by absolute address of data on the block device.
> -Users can easily change the partition.
> -
> -The format for the command line is just like mtdparts:
> -
> -blkdevparts=<blkdev-def>[;<blkdev-def>]
> +Authors: Cai Zhiyong <caizhiyong@huawei.com>
> +
> +The format for the command line is as follows,
> +it is used by MTD device (reference drivers/mtd/cmdlinepart.c) and
> +block device (reference block/partitions/cmdline.c)
> +
> +================================================================================
> +For MTD device:
> +  mtdparts=<mtddef>[;<mtddef]
> +  <mtddef>  := <mtd-id>:<partdef>[,<partdef>]
> +  <partdef> := <size>[@<offset>][<name>][ro][lk]
> +  <mtd-id>  := unique name used in mapping driver/device (mtd->name)
> +  <size>    := standard linux memsize OR "-" to denote all remaining space
> +               size is automatically truncated at end of device
> +               if specified or trucated size is 0 the part is skipped
> +  <offset>  := standard linux memsize
> +               if omitted the part will immediately follow the previous part
> +               or 0 if the first part
> +  <name>    := '(' NAME ')'
> +               NAME will appear in /proc/mtd
> +
> +  <size> and <offset> can be specified such that the parts are out of order
> +  in physical memory and may even overlap.
> +
> +  The parts are assigned MTD numbers in the order they are specified in the
> +  command line regardless of their order in physical memory.
> +
> +  Examples:
> +
> +  1 NOR Flash, with 1 single writable partition:
> +  edb7312-nor:-
> +
> +  1 NOR Flash with 2 partitions, 1 NAND with one
> +  edb7312-nor:256k(ARMboot)ro,-(root);edb7312-nand:-(home)
> +
> +================================================================================
> +For block device:
> +  blkdevparts=<blkdev-def>[;<blkdev-def>]
>    <blkdev-def> := <blkdev-id>:<partdef>[,<partdef>]
> -    <partdef> := <size>[@<offset>](part-name)
> -
> -<blkdev-id>
> -    block device disk name, embedded device used fixed block device,
> -    it's disk name also fixed. such as: mmcblk0, mmcblk1, mmcblk0boot0.
> -
> -<size>
> -    partition size, in bytes, such as: 512, 1m, 1G.
> -
> -<offset>
> -    partition start address, in bytes.
> -
> -(part-name)
> -    partition name, kernel send uevent with "PARTNAME". application can create
> -    a link to block device partition with the name "PARTNAME".
> -    user space application can access partition by partition name.
> -
> -Example:
> -    eMMC disk name is "mmcblk0" and "mmcblk0boot0"
> -
> -  bootargs:
> +  <partdef> := <size>[@<offset>][<name>]
> +  <blkdev-id>
> +       block device disk name, embedded device used fixed block device,
> +       it's disk name also fixed. such as: mmcblk0, mmcblk1, mmcblk0boot0.
> +  <size>    := standard linux memsize OR "-" to denote all remaining space
> +               size is automatically truncated at end of device
> +               if specified or trucated size is 0 the part is skipped
> +  <offset>  := standard linux memsize
> +               if omitted the part will immediately follow the previous part
> +               or 0 if the first part
> +  <name>    := '(' NAME ')'
> +        partition name, kernel send uevent with "PARTNAME". application could
> +        create a link to block device partition with the name "PARTNAME".
> +        user space application can access partition by partition name.
> +
> +  Example:
> +
> +    eMMC disk name is "mmcblk0" and "mmcblk0boot0", bootargs:
>      'blkdevparts=mmcblk0:1G(data0),1G(data1),-;mmcblk0boot0:1m(boot),-(kernel)'
> -
> -  dmesg:
> -    mmcblk0: p1(data0) p2(data1) p3()
> -    mmcblk0boot0: p1(boot) p2(kernel)
> -
> diff --git a/block/cmdline-parser.c b/block/cmdline-parser.c
> index 18fb435..8c09db3 100644
> --- a/block/cmdline-parser.c
> +++ b/block/cmdline-parser.c
> @@ -4,8 +4,6 @@
>   * Written by Cai Zhiyong <caizhiyong@huawei.com>
>   *
>   */
> -#include <linux/buffer_head.h>
> -#include <linux/module.h>

Hm.. this header removal seems an unrelated change, right?
I'd suggest to send a separate patch for this.

>  #include <linux/cmdline-parser.h>
>  
>  static int parse_subpart(struct cmdline_subpart **subpart, char *partdef)
> @@ -158,6 +156,7 @@ void cmdline_parts_free(struct cmdline_parts **parts)
>  		*parts = next_parts;
>  	}
>  }
> +EXPORT_SYMBOL(cmdline_parts_free);
>  
>  int cmdline_parts_parse(struct cmdline_parts **parts, const char *cmdline)
>  {
> @@ -205,6 +204,7 @@ fail:
>  	cmdline_parts_free(parts);
>  	goto done;
>  }
> +EXPORT_SYMBOL(cmdline_parts_parse);
>  
>  struct cmdline_parts *cmdline_parts_find(struct cmdline_parts *parts,
>  					 const char *bdev)
> @@ -213,16 +213,17 @@ struct cmdline_parts *cmdline_parts_find(struct cmdline_parts *parts,
>  		parts = parts->next_parts;
>  	return parts;
>  }
> +EXPORT_SYMBOL(cmdline_parts_find);
>  
>  /*
>   *  add_part()
>   *    0 success.
>   *    1 can not add so many partitions.
>   */
> -void cmdline_parts_set(struct cmdline_parts *parts, sector_t disk_size,
> -		       int slot,
> -		       int (*add_part)(int, struct cmdline_subpart *, void *),
> -		       void *param)
> +int cmdline_parts_set(struct cmdline_parts *parts, sector_t disk_size,
> +		      int slot,
> +		      int (*add_part)(int, struct cmdline_subpart *, void *),
> +		      void *param)
>  
>  {
>  	sector_t from = 0;
> @@ -246,4 +247,7 @@ void cmdline_parts_set(struct cmdline_parts *parts, sector_t disk_size,
>  		if (add_part(slot, subpart, param))
>  			break;
>  	}
> +
> +	return slot;
>  }
> +EXPORT_SYMBOL(cmdline_parts_set);
> diff --git a/drivers/mtd/Kconfig b/drivers/mtd/Kconfig
> index 5fab4e6e..6f7f9ca 100644
> --- a/drivers/mtd/Kconfig
> +++ b/drivers/mtd/Kconfig
> @@ -75,6 +75,7 @@ endif # MTD_REDBOOT_PARTS
>  
>  config MTD_CMDLINE_PARTS
>  	tristate "Command line partition table parsing"
> +	select CMDLINE_PARSER
>  	depends on MTD
>  	---help---
>  	  Allow generic configuration of the MTD partition tables via the kernel
> diff --git a/drivers/mtd/cmdlinepart.c b/drivers/mtd/cmdlinepart.c
> index 721caeb..79bd584 100644
> --- a/drivers/mtd/cmdlinepart.c
> +++ b/drivers/mtd/cmdlinepart.c
> @@ -18,34 +18,8 @@
>   * along with this program; if not, write to the Free Software
>   * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
>   *
> - * The format for the command line is as follows:
> + * Verbose please reference "Documentation/block/cmdline-partition.txt"
>   *
> - * mtdparts=<mtddef>[;<mtddef]
> - * <mtddef>  := <mtd-id>:<partdef>[,<partdef>]
> - * <partdef> := <size>[@<offset>][<name>][ro][lk]
> - * <mtd-id>  := unique name used in mapping driver/device (mtd->name)
> - * <size>    := standard linux memsize OR "-" to denote all remaining space
> - *              size is automatically truncated at end of device
> - *              if specified or trucated size is 0 the part is skipped
> - * <offset>  := standard linux memsize
> - *              if omitted the part will immediately follow the previous part
> - *              or 0 if the first part
> - * <name>    := '(' NAME ')'
> - *              NAME will appear in /proc/mtd
> - *
> - * <size> and <offset> can be specified such that the parts are out of order
> - * in physical memory and may even overlap.
> - *
> - * The parts are assigned MTD numbers in the order they are specified in the
> - * command line regardless of their order in physical memory.
> - *
> - * Examples:
> - *
> - * 1 NOR Flash, with 1 single writable partition:
> - * edb7312-nor:-
> - *
> - * 1 NOR Flash with 2 partitions, 1 NAND with one
> - * edb7312-nor:256k(ARMboot)ro,-(root);edb7312-nand:-(home)
>   */
>  
>  #include <linux/kernel.h>
> @@ -54,249 +28,43 @@
>  #include <linux/mtd/partitions.h>
>  #include <linux/module.h>
>  #include <linux/err.h>
> +#include <linux/cmdline-parser.h>
>  
> -/* error message prefix */
> -#define ERRP "mtd: "
> -
> -/* debug macro */
> -#if 0
> -#define dbg(x) do { printk("DEBUG-CMDLINE-PART: "); printk x; } while(0)
> -#else
> -#define dbg(x)
> -#endif
> -
> -
> -/* special size referring to all the remaining space in a partition */
> -#define SIZE_REMAINING ULLONG_MAX
> -#define OFFSET_CONTINUOUS ULLONG_MAX
> -
> -struct cmdline_mtd_partition {
> -	struct cmdline_mtd_partition *next;
> -	char *mtd_id;
> -	int num_parts;
> -	struct mtd_partition *parts;
> -};
> -
> -/* mtdpart_setup() parses into here */
> -static struct cmdline_mtd_partition *partitions;
> -
> -/* the command line passed to mtdpart_setup() */
>  static char *mtdparts;
> -static char *cmdline;
> -static int cmdline_parsed;
> +static struct cmdline_parts *mtd_cmdline_parts;
>  
> -/*
> - * Parse one partition definition for an MTD. Since there can be many
> - * comma separated partition definitions, this function calls itself
> - * recursively until no more partition definitions are found. Nice side
> - * effect: the memory to keep the mtd_partition structs and the names
> - * is allocated upon the last definition being found. At that point the
> - * syntax has been verified ok.
> - */
> -static struct mtd_partition * newpart(char *s,
> -				      char **retptr,
> -				      int *num_parts,
> -				      int this_part,
> -				      unsigned char **extra_mem_ptr,
> -				      int extra_mem_size)
> +static int add_part(int slot, struct cmdline_subpart *subpart, void *param)
>  {
> -	struct mtd_partition *parts;
> -	unsigned long long size, offset = OFFSET_CONTINUOUS;
> -	char *name;
> -	int name_len;
> -	unsigned char *extra_mem;
> -	char delim;
> -	unsigned int mask_flags;
> -
> -	/* fetch the partition size */
> -	if (*s == '-') {
> -		/* assign all remaining space to this partition */
> -		size = SIZE_REMAINING;
> -		s++;
> -	} else {
> -		size = memparse(s, &s);
> -		if (size < PAGE_SIZE) {
> -			printk(KERN_ERR ERRP "partition size too small (%llx)\n",
> -			       size);
> -			return ERR_PTR(-EINVAL);
> -		}
> -	}
> +	struct mtd_partition *mtdpart = &((struct mtd_partition *)param)[slot];
>  
> -	/* fetch partition name and flags */
> -	mask_flags = 0; /* this is going to be a regular partition */
> -	delim = 0;
> +	mtdpart->offset = subpart->from;
> +	mtdpart->size = subpart->size;
> +	mtdpart->name = subpart->name;
> +	mtdpart->mask_flags = 0;
>  
> -	/* check for offset */
> -	if (*s == '@') {
> -		s++;
> -		offset = memparse(s, &s);
> -	}
> -
> -	/* now look for name */
> -	if (*s == '(')
> -		delim = ')';
> -
> -	if (delim) {
> -		char *p;
> -
> -		name = ++s;
> -		p = strchr(name, delim);
> -		if (!p) {
> -			printk(KERN_ERR ERRP "no closing %c found in partition name\n", delim);
> -			return ERR_PTR(-EINVAL);
> -		}
> -		name_len = p - name;
> -		s = p + 1;
> -	} else {
> -		name = NULL;
> -		name_len = 13; /* Partition_000 */
> -	}
> -
> -	/* record name length for memory allocation later */
> -	extra_mem_size += name_len + 1;
> -
> -	/* test for options */
> -	if (strncmp(s, "ro", 2) == 0) {
> -		mask_flags |= MTD_WRITEABLE;
> -		s += 2;
> -	}
> +	if (subpart->flags & PF_RDONLY)
> +		mtdpart->mask_flags |= MTD_WRITEABLE;
>  
>  	/* if lk is found do NOT unlock the MTD partition*/
> -	if (strncmp(s, "lk", 2) == 0) {
> -		mask_flags |= MTD_POWERUP_LOCK;
> -		s += 2;
> -	}
> -
> -	/* test if more partitions are following */
> -	if (*s == ',') {
> -		if (size == SIZE_REMAINING) {
> -			printk(KERN_ERR ERRP "no partitions allowed after a fill-up partition\n");
> -			return ERR_PTR(-EINVAL);
> -		}
> -		/* more partitions follow, parse them */
> -		parts = newpart(s + 1, &s, num_parts, this_part + 1,
> -				&extra_mem, extra_mem_size);
> -		if (IS_ERR(parts))
> -			return parts;
> -	} else {
> -		/* this is the last partition: allocate space for all */
> -		int alloc_size;
> -
> -		*num_parts = this_part + 1;
> -		alloc_size = *num_parts * sizeof(struct mtd_partition) +
> -			     extra_mem_size;
> -
> -		parts = kzalloc(alloc_size, GFP_KERNEL);
> -		if (!parts)
> -			return ERR_PTR(-ENOMEM);
> -		extra_mem = (unsigned char *)(parts + *num_parts);
> -	}
> -
> -	/* enter this partition (offset will be calculated later if it is zero at this point) */
> -	parts[this_part].size = size;
> -	parts[this_part].offset = offset;
> -	parts[this_part].mask_flags = mask_flags;
> -	if (name)
> -		strlcpy(extra_mem, name, name_len + 1);
> -	else
> -		sprintf(extra_mem, "Partition_%03d", this_part);
> -	parts[this_part].name = extra_mem;
> -	extra_mem += name_len + 1;
> -
> -	dbg(("partition %d: name <%s>, offset %llx, size %llx, mask flags %x\n",
> -	     this_part, parts[this_part].name, parts[this_part].offset,
> -	     parts[this_part].size, parts[this_part].mask_flags));
> +	if (subpart->flags & PF_POWERUP_LOCK)
> +		mtdpart->mask_flags |= MTD_POWERUP_LOCK;
>  
> -	/* return (updated) pointer to extra_mem memory */
> -	if (extra_mem_ptr)
> -		*extra_mem_ptr = extra_mem;
> -
> -	/* return (updated) pointer command line string */
> -	*retptr = s;
> -
> -	/* return partition table */
> -	return parts;
> +	return 0;
>  }
>  
>  /*
> - * Parse the command line.
> + * This is the handler for our kernel parameter, called from
> + * main.c::checksetup(). Note that we can not yet kmalloc() anything,
> + * so we only save the commandline for later processing.
> + *
> + * This function needs to be visible for bootloaders.
>   */
> -static int mtdpart_setup_real(char *s)
> +static int __init mtdpart_setup(char *s)
>  {
> -	cmdline_parsed = 1;
> -
> -	for( ; s != NULL; )
> -	{
> -		struct cmdline_mtd_partition *this_mtd;
> -		struct mtd_partition *parts;
> -		int mtd_id_len, num_parts;
> -		char *p, *mtd_id;
> -
> -		mtd_id = s;
> -
> -		/* fetch <mtd-id> */
> -		p = strchr(s, ':');
> -		if (!p) {
> -			printk(KERN_ERR ERRP "no mtd-id\n");
> -			return -EINVAL;
> -		}
> -		mtd_id_len = p - mtd_id;
> -
> -		dbg(("parsing <%s>\n", p+1));
> -
> -		/*
> -		 * parse one mtd. have it reserve memory for the
> -		 * struct cmdline_mtd_partition and the mtd-id string.
> -		 */
> -		parts = newpart(p + 1,		/* cmdline */
> -				&s,		/* out: updated cmdline ptr */
> -				&num_parts,	/* out: number of parts */
> -				0,		/* first partition */
> -				(unsigned char**)&this_mtd, /* out: extra mem */
> -				mtd_id_len + 1 + sizeof(*this_mtd) +
> -				sizeof(void*)-1 /*alignment*/);
> -		if (IS_ERR(parts)) {
> -			/*
> -			 * An error occurred. We're either:
> -			 * a) out of memory, or
> -			 * b) in the middle of the partition spec
> -			 * Either way, this mtd is hosed and we're
> -			 * unlikely to succeed in parsing any more
> -			 */
> -			 return PTR_ERR(parts);
> -		 }
> -
> -		/* align this_mtd */
> -		this_mtd = (struct cmdline_mtd_partition *)
> -				ALIGN((unsigned long)this_mtd, sizeof(void *));
> -		/* enter results */
> -		this_mtd->parts = parts;
> -		this_mtd->num_parts = num_parts;
> -		this_mtd->mtd_id = (char*)(this_mtd + 1);
> -		strlcpy(this_mtd->mtd_id, mtd_id, mtd_id_len + 1);
> -
> -		/* link into chain */
> -		this_mtd->next = partitions;
> -		partitions = this_mtd;
> -
> -		dbg(("mtdid=<%s> num_parts=<%d>\n",
> -		     this_mtd->mtd_id, this_mtd->num_parts));
> -
> -
> -		/* EOS - we're done */
> -		if (*s == 0)
> -			break;
> -
> -		/* does another spec follow? */
> -		if (*s != ';') {
> -			printk(KERN_ERR ERRP "bad character after partition (%c)\n", *s);
> -			return -EINVAL;
> -		}
> -		s++;
> -	}
> -
> -	return 0;
> +	mtdparts = s;
> +	return 1;
>  }
> +__setup("mtdparts=", mtdpart_setup);
>  
>  /*
>   * Main function to be called from the MTD mapping driver/device to
> @@ -309,82 +77,35 @@ static int parse_cmdline_partitions(struct mtd_info *master,
>  				    struct mtd_partition **pparts,
>  				    struct mtd_part_parser_data *data)
>  {
> -	unsigned long long offset;
> -	int i, err;
> -	struct cmdline_mtd_partition *part;
> -	const char *mtd_id = master->name;
> +	struct cmdline_parts *parts;
>  
> -	/* parse command line */
> -	if (!cmdline_parsed) {
> -		err = mtdpart_setup_real(cmdline);
> -		if (err)
> -			return err;
> -	}
> +	if (mtdparts) {
> +		if (mtd_cmdline_parts)
> +			cmdline_parts_free(&mtd_cmdline_parts);
> +
> +		if (cmdline_parts_parse(&mtd_cmdline_parts, mtdparts)) {
> +			mtdparts = NULL;
> +			return -EINVAL;
> +		}
>  
> -	/*
> -	 * Search for the partition definition matching master->name.
> -	 * If master->name is not set, stop at first partition definition.
> -	 */
> -	for (part = partitions; part; part = part->next) {
> -		if ((!mtd_id) || (!strcmp(part->mtd_id, mtd_id)))
> -			break;
> +		mtdparts = NULL;
>  	}
>  
> -	if (!part)
> +	if (!mtd_cmdline_parts)
>  		return 0;
>  
> -	for (i = 0, offset = 0; i < part->num_parts; i++) {
> -		if (part->parts[i].offset == OFFSET_CONTINUOUS)
> -			part->parts[i].offset = offset;
> -		else
> -			offset = part->parts[i].offset;
> -
> -		if (part->parts[i].size == SIZE_REMAINING)
> -			part->parts[i].size = master->size - offset;
> -
> -		if (offset + part->parts[i].size > master->size) {
> -			printk(KERN_WARNING ERRP
> -			       "%s: partitioning exceeds flash size, truncating\n",
> -			       part->mtd_id);
> -			part->parts[i].size = master->size - offset;
> -		}
> -		offset += part->parts[i].size;
> -
> -		if (part->parts[i].size == 0) {
> -			printk(KERN_WARNING ERRP
> -			       "%s: skipping zero sized partition\n",
> -			       part->mtd_id);
> -			part->num_parts--;
> -			memmove(&part->parts[i], &part->parts[i + 1],
> -				sizeof(*part->parts) * (part->num_parts - i));
> -			i--;
> -		}
> -	}
> +	parts = cmdline_parts_find(mtd_cmdline_parts, master->name);
> +	if (!parts)
> +		return 0;
>  
> -	*pparts = kmemdup(part->parts, sizeof(*part->parts) * part->num_parts,
> -			  GFP_KERNEL);
> +	*pparts = kzalloc(sizeof(**pparts) * parts->nr_subparts, GFP_KERNEL);
>  	if (!*pparts)
>  		return -ENOMEM;
>  
> -	return part->num_parts;
> -}
> -
> -
> -/*
> - * This is the handler for our kernel parameter, called from
> - * main.c::checksetup(). Note that we can not yet kmalloc() anything,
> - * so we only save the commandline for later processing.
> - *
> - * This function needs to be visible for bootloaders.
> - */
> -static int __init mtdpart_setup(char *s)
> -{
> -	cmdline = s;
> -	return 1;
> +	return cmdline_parts_set(parts, master->size, 0, add_part,
> +				 (void *)*pparts);
>  }
>  
> -__setup("mtdparts=", mtdpart_setup);
> -
>  static struct mtd_part_parser cmdline_parser = {
>  	.owner = THIS_MODULE,
>  	.parse_fn = parse_cmdline_partitions,
> @@ -393,8 +114,6 @@ static struct mtd_part_parser cmdline_parser = {
>  
>  static int __init cmdline_parser_init(void)
>  {
> -	if (mtdparts)
> -		mtdpart_setup(mtdparts);
>  	return register_mtd_parser(&cmdline_parser);
>  }
>  
> diff --git a/include/linux/cmdline-parser.h b/include/linux/cmdline-parser.h
> index 98e892e..43b65a9 100644
> --- a/include/linux/cmdline-parser.h
> +++ b/include/linux/cmdline-parser.h
> @@ -35,9 +35,9 @@ int cmdline_parts_parse(struct cmdline_parts **parts, const char *cmdline);
>  struct cmdline_parts *cmdline_parts_find(struct cmdline_parts *parts,
>  					 const char *bdev);
>  
> -void cmdline_parts_set(struct cmdline_parts *parts, sector_t disk_size,
> -		       int slot,
> -		       int (*add_part)(int, struct cmdline_subpart *, void *),
> -		       void *param);
> +int cmdline_parts_set(struct cmdline_parts *parts, sector_t disk_size,
> +		      int slot,
> +		      int (*add_part)(int, struct cmdline_subpart *, void *),
> +		      void *param);
>  
>  #endif /* CMDLINEPARSEH */
> -- 
> 1.8.1.5
> 

I'd like to review the patch in detail and test it, but being a bit old,
the patch doesn't apply as it is on v3.12-rc5. Care to resend an update?

Brian: I saw you want to move forward with this. I guess we can give
it a test, and if all the possible 'mtdparts' use cases work, then
we shouldn't object the cleanup, right?
-- 
Ezequiel García, Free Electrons
Embedded Linux, Kernel and Android Engineering
http://free-electrons.com