The devtool modify
command prepares the
way to work on existing code that already has a recipe in
place.
The command is flexible enough to allow you to extract code,
specify the existing recipe, and keep track of and gather any
patch files from other developers that are
associated with the code.
Depending on your particular scenario, the arguments and options
you use with devtool modify
form different
combinations.
The following diagram shows common development flows
you would use with the devtool modify
command:
Preparing to Modify the Code:
The top part of the flow shows three scenarios by which
you could use devtool modify
to
prepare to work on source files.
Each scenario assumes the following:
The recipe exists in some layer external
to the devtool
workspace.
The source files exist upstream in an un-extracted state or locally in a previously extracted state.
The typical situation is where another developer has created some layer for use with the Yocto Project and their recipe already resides in that layer. Furthermore, their source code is readily available either upstream or locally.
Left:
The left scenario represents a common situation
where the source code does not exist locally
and needs to be extracted.
In this situation, the source is extracted
into the default workspace location.
The recipe, in this scenario, is in its own
layer outside the workspace
(i.e.
meta-
layername
).
The following command identifies the recipe and by default extracts the source files:
$ devtool modify recipe
Once devtool
locates the recipe,
it uses the
SRC_URI
variable to locate the source code and
any local patch files from other developers are
located.
srctree
when using the
devtool modify
command.
With this scenario, however, since no
srctree
argument exists, the
devtool modify
command by default
extracts the source files to a Git structure.
Furthermore, the location for the extracted source is the
default area within the workspace.
The result is that the command sets up both the source
code and an append file within the workspace with the
recipe remaining in its original location.
Middle: The middle scenario represents a situation where the source code also does not exist locally. In this case, the code is again upstream and needs to be extracted to some local area as a Git repository. The recipe, in this scenario, is again in its own layer outside the workspace.
The following command tells
devtool
what recipe with
which to work and, in this case, identifies a local
area for the extracted source files that is outside
of the default workspace:
$ devtool modify recipe srctree
As with all extractions, the command uses
the recipe's SRC_URI
to locate the
source files.
Once the files are located, the command by default
extracts them.
Providing the srctree
argument instructs devtool
where
place the extracted source.
Within workspace, devtool
creates an append file for the recipe.
The recipe remains in its original location but
the source files are extracted to the location you
provided with srctree
.
Right:
The right scenario represents a situation
where the source tree
(srctree
) exists as a
previously extracted Git structure outside of
the devtool
workspace.
In this example, the recipe also exists
elsewhere in its own layer.
The following command tells
devtool
the recipe
with which to work, uses the "-n" option to indicate
source does not need to be extracted, and uses
srctree
to point to the
previously extracted source files:
$ devtool modify -n recipe srctree
Once the command finishes, it creates only an append file for the recipe in the workspace. The recipe and the source code remain in their original locations.
Edit the Source:
Once you have used the devtool modify
command, you are free to make changes to the source
files.
You can use any editor you like to make and save
your source code modifications.
Build the Recipe:
Once you have updated the source files, you can build
the recipe.
You can either use devtool build
or
bitbake
.
Either method produces build output that is stored
in
TMPDIR
.
Deploy the Build Output:
When you use the devtool build
command or bitbake
to build out your
recipe, you probably want to see if the resulting build
output works as expected on target hardware.
You can deploy your build output to that target hardware by
using the devtool deploy-target
command:
$ devtool deploy-target recipe target
The target
is a live target machine
running as an SSH server.
You can, of course, also deploy the image you build
using the devtool build-image
command
to actual hardware.
However, devtool
does not provide a
specific command that allows you to do this.
Optionally Create Patch Files for Your Changes:
After you have debugged your changes, you can
use devtool update-recipe
to
generate patch files for all the commits you have
made.
$ devtool update-recipe recipe
By default, the
devtool update-recipe
command
creates the patch files in a folder named the same
as the recipe beneath the folder in which the recipe
resides, and updates the recipe's
SRC_URI
statement to point to the generated patch files.
LAYERDIR
"
option to cause the command to create append files
in a specific layer rather than the default
recipe layer.
Restore the Workspace:
The devtool reset
restores the
state so that standard layers and upstream sources are
used to build the recipe rather than what is in the
workspace.
$ devtool reset recipe