Stream User’s Guide

7.10Component main

Source file components/main.c defines the main of the component version of the demo application. This section walks through the source to explain its use of the Stream programming model; error handling code is elided here. main loads a DSP MIPS image, creates three component instances, creates two connections between them, and then sends three commands, as shown below.





main first starts the Stream programming model runtime:

spi_spm_start("spm_demo", &argc, argv, SPI_SPM_FLAG_NONE);



main processes its argc/argv after this call, not before, since spi_spm_start may adjust argc/argv, removing special SPM runtime options from the program’s argument list. Then main loads a DSP MIPS image, passing it an argument to set the debug log enable mask to 0xf.

if (spi_load_image(SPI_PEL_DSP_MIPS, image,

dsp_argv, NULL, SPI_IMAGE_FLAG_NONE)!= 0) {

...

It then finds each of the three components required by the application (file input, green screen removal, and file output) and creates an instance of each component.

file_in = spi_component_find("spi_example_filein",

SPI_PROVIDER_SPI, NULL, NULL);

file_out = spi_component_find("spi_example_fileout",

SPI_PROVIDER_SPI, NULL, NULL);

gsr = spi_component_find("spi_example_gsr",

SPI_PROVIDER_SPI, NULL, NULL);

...
/* Create one instance of each component. */

i0 = spi_instance_new("in0", file_in);

o0 = spi_instance_new("out0", file_out);

g0 = spi_instance_new("gsr0", gsr);

...
Next, it defines the plumbing to connect the components: the file input component output port connects to the green screen reduction component input port, and the green screen reduction component output port connects to the file output component input.

spi_connection_t in_to_gsr = spi_connect("file_in_to_gsr",

i0, FILE_IN_PORT_OUT,

g0, SPI_GSR_PORT_IN,

1 /* depth */);

spi_connection_t gsr_to_out = spi_connect("gsr_to_file_out",

g0, SPI_GSR_PORT_OUT,

o0, FILE_OUT_PORT_IN,

1 /* depth */);

...
To start the ball rolling, the application issues a FILE_IN_CMD_FILENAME command to the file input component, passing the input filename in the command payload. If the response to the command is not SPI_RESPONSE_ERRNO_OK, the application fails.

* Send the input filename to the file in instance.

* The FILE_IN_CMD_PAYLOAD is the filename string including the

* '\0' terminator.

*/

response = spi_cmd_send(i0, FILE_IN_CMD_FILENAME,

if (spi_response_get_errno(response) != SPI_RESPONSE_ERRNO_OK) {

fatal("setting input filename: %s",

spi_response_strerror(spi_response_get_errno(response)));

}

spi_response_free(response);

/* Send the output filename to the file out instance. */

response = spi_cmd_send(o0, FILE_OUT_CMD_FILENAME,

(void *)outfile, strlen(outfile) + 1);

if (spi_response_get_errno(response) != SPI_RESPONSE_ERRNO_OK) {

fatal("setting output filename: %s",

spi_response_strerror(spi_response_get_errno(response)));

}

spi_response_free(response);

response = spi_cmd_send(o0, FILE_OUT_CMD_REPORT_WRITTEN, NULL, 0);

if (spi_response_get_errno(response) != SPI_RESPONSE_ERRNO_OK) {

fatal("waiting for file write: %s",

spi_response_strerror(spi_response_get_errno(response)));

}

spi_response_free(response);

7.10.1Initialization file

Instead of writing explicit initialization code as described in the previous section, including tedious error checking, the programmer can provide a simple initialization file as described in Initialization files above. The initialization code in components/main.c is conditionalized #if !defined(INIT_FILE). If it is compiled with spc -D INIT_FILE, the source does not use the explicit initialization code, but rather assumes that the user will invoke the System MIPS application with a command line initialization file option:

$ ./spm_demo.init.sys.out --spi_init_file=init.xml
Initialization file init.xml contains statements that load the target image on DSP MIPS, create instances, create connections between instances, and issue initialization commands to instances; see the diagram in the preceding Component main section.








from="i0:FILE_IN_PORT_OUT" to="g0:GSR_PORT_IN" />

from="g0:GSR_PORT_OUT" to="o0:FILE_OUT_PORT_IN" />

The remaining source in main in components/main.c is extremely simple: it just calls spi_spm_start and spi_spm_stop, letting the initialization file processing by spi_spm_start do all the work.
The next chapter explains how to build and run the complete spm_demo application from the command line.

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