The final value of "BBFILES" is:

/home/yocto/master/build/recipes/images/custom/*.bb
/home/yocto/master/build/recipes/images/*.bb
/home/yocto/_poky_master.toaster_cloned/meta/recipes-*/*/*.bb
/home/yocto/_poky_master.toaster_cloned/meta-yocto/recipes-*/*/*.bb
/home/yocto/_poky_master.toaster_cloned/meta-yocto/recipes-*/*/*.bbappend
/home/yocto/_poky_master.toaster_cloned/meta-yocto-bsp/recipes-*/*/*.bb
/home/yocto/_poky_master.toaster_cloned/meta-yocto-bsp/recipes-*/*/*.bbappend

The pre-expanded value of "BBFILES" is:

${TOPDIR}/recipes/images/custom/*.bb
${TOPDIR}/recipes/images/*.bb
/home/yocto/_poky_master.toaster_cloned/meta/recipes-*/*/*.bb
/home/yocto/_poky_master.toaster_cloned/meta-yocto/recipes-*/*/*.bb
/home/yocto/_poky_master.toaster_cloned/meta-yocto/recipes-*/*/*.bbappend
/home/yocto/_poky_master.toaster_cloned/meta-yocto-bsp/recipes-*/*/*.bb
/home/yocto/_poky_master.toaster_cloned/meta-yocto-bsp/recipes-*/*/*.bbappend

About "BBFILES"

List of recipe files used by BitBake to build software.

Read more about this variable in the Yocto Project manual

"BBFILES" history

Order File Line number Operation
1 build/conf/bblayers.conf 6 Soft set (?=)
""
# LAYER_CONF_VERSION is increased each time build/conf/bblayers.conf
# changes incompatibly
LCONF_VERSION = "6"

BBPATH = "${TOPDIR}"
BBFILES ?= ""

#BBLAYERS ?= " \
#  /home/yocto/_poky_master.toaster_cloned/meta \
#  /home/yocto/_poky_master.toaster_cloned/meta-yocto \
#  /home/yocto/_poky_master.toaster_cloned/meta-yocto-bsp \
2 build/conf/bblayers.conf 18 Append (+=)
${TOPDIR}/recipes/images/custom/*.bb
BBLAYERS_NON_REMOVABLE ?= " \
  /home/yocto/_poky_master.toaster_cloned/meta \
  /home/yocto/_poky_master.toaster_cloned/meta-yocto \
  "
#added by hob
BBFILES += "${TOPDIR}/recipes/images/custom/*.bb"
#added by hob
BBFILES += "${TOPDIR}/recipes/images/*.bb"

#added by hob
BBLAYERS = "/home/yocto/_poky_master.toaster_cloned/meta /home/yocto/_poky_master.toaster_cloned/meta-yocto /home/yocto/_poky_master.toaster_cloned/meta-yocto-bsp"
3 build/conf/bblayers.conf 20 Append (+=)
${TOPDIR}/recipes/images/custom/*.bb
${TOPDIR}/recipes/images/*.bb
/home/yocto/_poky_master.toaster_cloned/meta-yocto \
"
#added by hob
BBFILES += "${TOPDIR}/recipes/images/custom/*.bb"
#added by hob
BBFILES += "${TOPDIR}/recipes/images/*.bb"

#added by hob
BBLAYERS = "/home/yocto/_poky_master.toaster_cloned/meta /home/yocto/_poky_master.toaster_cloned/meta-yocto /home/yocto/_poky_master.toaster_cloned/meta-yocto-bsp"
# line added by toaster build control
BBLAYERS = "/home/yocto/_poky_fido.toaster_cloned/meta /home/yocto/_poky_fido.toaster_cloned/meta-yocto /home/yocto/_poky_fido.toaster_cloned/meta-yocto-bsp"
4 meta/conf/layer.conf 4 Append (+=)
${TOPDIR}/recipes/images/custom/*.bb
${TOPDIR}/recipes/images/*.bb
${LAYERDIR}/recipes-*/*/*.bb
# We have a conf and classes directory, add to BBPATH
BBPATH .= ":${LAYERDIR}"
# We have recipes-* directories, add to BBFILES
BBFILES += "${LAYERDIR}/recipes-*/*/*.bb"

BBFILE_COLLECTIONS += "core"
BBFILE_PATTERN_core = "^${LAYERDIR}/"
BBFILE_PRIORITY_core = "5"

5 bitbake/lib/bb/data_smart.py 741 Expand
${TOPDIR}/recipes/images/custom/*.bb
${TOPDIR}/recipes/images/*.bb
/home/yocto/_poky_master.toaster_cloned/meta/recipes-*/*/*.bb
ref = '${%s}' % variable
value = self.getVar(variable, False)
for key in keys:
	referrervalue = self.getVar(key, False)
	if referrervalue and ref in referrervalue:
		self.setVar(key, referrervalue.replace(ref, value))

def localkeys(self):
	for key in self.dict:
		if key != '_data':
			yield key
6 meta-yocto/conf/layer.conf 6 Append (+=)
${TOPDIR}/recipes/images/custom/*.bb
${TOPDIR}/recipes/images/*.bb
/home/yocto/_poky_master.toaster_cloned/meta/recipes-*/*/*.bb
${LAYERDIR}/recipes-*/*/*.bb
${LAYERDIR}/recipes-*/*/*.bbappend
# We have a conf and classes directory, add to BBPATH
BBPATH =. "${LAYERDIR}:"

# We have recipes-* directories, add to BBFILES
BBFILES += "${LAYERDIR}/recipes-*/*/*.bb \
			${LAYERDIR}/recipes-*/*/*.bbappend"

BBFILE_COLLECTIONS += "yocto"
BBFILE_PATTERN_yocto = "^${LAYERDIR}/"
BBFILE_PRIORITY_yocto = "5"

7 bitbake/lib/bb/data_smart.py 741 Expand
${TOPDIR}/recipes/images/custom/*.bb
${TOPDIR}/recipes/images/*.bb
/home/yocto/_poky_master.toaster_cloned/meta/recipes-*/*/*.bb
/home/yocto/_poky_master.toaster_cloned/meta-yocto/recipes-*/*/*.bb
/home/yocto/_poky_master.toaster_cloned/meta-yocto/recipes-*/*/*.bbappend
ref = '${%s}' % variable
value = self.getVar(variable, False)
for key in keys:
	referrervalue = self.getVar(key, False)
	if referrervalue and ref in referrervalue:
		self.setVar(key, referrervalue.replace(ref, value))

def localkeys(self):
for key in self.dict:
	if key != '_data':
		yield key
8 meta-yocto-bsp/conf/layer.conf 6 Append (+=)
${TOPDIR}/recipes/images/custom/*.bb
${TOPDIR}/recipes/images/*.bb
/home/yocto/_poky_master.toaster_cloned/meta/recipes-*/*/*.bb
/home/yocto/_poky_master.toaster_cloned/meta-yocto/recipes-*/*/*.bb
/home/yocto/_poky_master.toaster_cloned/meta-yocto/recipes-*/*/*.bbappend
${LAYERDIR}/recipes-*/*/*.bb
${LAYERDIR}/recipes-*/*/*.bbappend
# We have a conf and classes directory, add to BBPATH
BBPATH .= ":${LAYERDIR}"

# We have recipes-* directories, add to BBFILES
BBFILES += "${LAYERDIR}/recipes-*/*/*.bb \
		    ${LAYERDIR}/recipes-*/*/*.bbappend"

BBFILE_COLLECTIONS += "yoctobsp"
BBFILE_PATTERN_yoctobsp = "^${LAYERDIR}/"
BBFILE_PRIORITY_yoctobsp = "5"
LAYERVERSION_yoctobsp = "3"
9 bitbake/lib/bb/data_smart.py 741 Expand
${TOPDIR}/recipes/images/custom/*.bb
${TOPDIR}/recipes/images/*.bb
/home/yocto/_poky_master.toaster_cloned/meta/recipes-*/*/*.bb
/home/yocto/_poky_master.toaster_cloned/meta-yocto/recipes-*/*/*.bb
/home/yocto/_poky_master.toaster_cloned/meta-yocto/recipes-*/*/*.bbappend
/home/yocto/_poky_master.toaster_cloned/meta-yocto-bsp/recipes-*/*/*.bb
/home/yocto/_poky_master.toaster_cloned/meta-yocto-bsp/recipes-*/*/*.bbappend
ref = '${%s}' % variable
value = self.getVar(variable, False)
for key in keys:
	referrervalue = self.getVar(key, False)
	if referrervalue and ref in referrervalue:
		self.setVar(key, referrervalue.replace(ref, value))

def localkeys(self):
	for key in self.dict:
		if key != '_data':
			yield key
10 bitbake/lib/bb/cooker.py 1618 Set
/home/yocto/master/build/recipes/images/custom/*.bb
/home/yocto/master/build/recipes/images/*.bb
/home/yocto/_poky_master.toaster_cloned/meta/recipes-*/*/*.bb
/home/yocto/_poky_master.toaster_cloned/meta-yocto/recipes-*/*/*.bb
/home/yocto/_poky_master.toaster_cloned/meta-yocto/recipes-*/*/*.bbappend
/home/yocto/_poky_master.toaster_cloned/meta-yocto-bsp/recipes-*/*/*.bb
masked = 0

collectlog.debug(1, "collecting .bb files")

files = (config.getVar( "BBFILES", True) or "").split()
config.setVar("BBFILES", " ".join(files))

# Sort files by priority
files.sort( key=lambda fileitem: self.calc_bbfile_priority(fileitem) )

if not len(files):