HOWTO_build_your_own_module

本文详细介绍如何在嵌入式Linux环境下为特定传感器编写驱动程序。包括如何在内核源码树中添加自定义配置项及模块参数设置,并提供具体步骤如修改Kconfig文件和Makefile来实现模块加载。

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<1>>>In kernel code tree:
     aa>>>update Kconfig, eg: drivers/sensors/Kconfig中加入一行,引入自己的Kconfig:
source "drivers/sensors/Kconfig"
     ab>>>your kconfig in subdir, drivers/sensors/Kconfig, example:
menuconfig SENSORS
        tristate "Sensors class support"
         default n
        ---help---
          Say Y here to enable sensors class support. This allows
          user manipulate the sensors from sysfs interface.

if SENSORS
 
config SENSORS_AKM8975
    tristate "AKM8975/C Compass-senseor Driver"
    default n
    ---help---
      Say Y here if you want to enable the AKM8975/C compass-sensor

endif # SENSORS
    ba>>>update Makefile:
    >obj-m += sensors/
.or.
    >obj-$(CONFIG_SENSORS_AKM8975) += sensors/
    bb>>>update Makefile in subdir:
        >obj-m := akm8975_sensors.o
       .or.
        >obj-$(CONFIG_SENSORS_AKM8975) := akm8975_sensors.o
p.s. module_param(name, type, perm);
           1 The type argument holds the parameter's data type; it is one of byte, short, ushort, int, uint, long, ulong, charp, bool, or invbool. 

           2 the perm argument specifies the permissions of the corresponding file in sysfs.

<2>>>Outside kernel code tree, 只需要编写一个Makefile即可:

ifeq ($(KERNELRELEASE),)
modules:
           $(MAKE) -C /home/sudolee/workstation/kernel-2.6.32/ M=$(shell pwd) $@

else
          obj-m := debugfs.o
endif

clean:
          rm -f *.o *.cmd *.mod.* modules.order Module.symvers *.ko .*.cmd
          rm -rf .tmp_versions/
.PHONY:modules clean


### UVM Config_DB Usage for AXI Slave Configuration In Universal Verification Methodology (UVM), configuring components like an AXI slave involves setting up parameters that define how this component operates within a testbench environment. The `uvm_config_db` mechanism facilitates passing configurations between different parts of the verification system without requiring direct connections or dependencies. For an AXI slave configuration using `uvm_config_db`, one would typically follow these steps: #### Setting Up Configuration Data To configure an AXI slave, specific settings such as base address, memory map details, and other operational parameters need to be established before simulation starts. This can be done by calling `uvm_config_db::set()` with appropriate arguments specifying context (`cntxt`), instance name (`inst_name`), field name (`field_name`), and value[^2]. ```cpp // Example setup code snippet in top-level module or initial block. initial begin // Assuming 'axi_slave_base_addr' holds the desired starting point for addressing. int axi_slave_base_addr = 32'h8000_0000; // Set the base address into config database under "uvm_test_top.env.axi_slv_agent". uvm_config_db #(int)::set(null, "uvm_test_top.env.axi_slv_agent", "base_address", axi_slave_base_addr); end ``` This example demonstrates storing an integer representing the base address associated with `"uvm_test_top.env.axi_slv_agent"` named `"base_address"`. #### Retrieving Configuration Within Components Within the AXI slave agent or driver/sequencer classes, retrieve previously stored values through calls to `uvm_config_db::get()`. Here’s how it might look inside a constructor or build phase method where initialization occurs: ```cpp class axi_slave_driver extends uvm_driver #(axi_transaction); protected int m_base_address; function new(string name, uvm_component parent); super.new(name,parent); if (!uvm_config_db #(int)::get(this,"","base_address",m_base_address)) begin `uvm_fatal("NO_CFG",{"Configuration item not found: ", get_full_name(), ".base_address"}) end `uvm_info(get_type_name(),$sformatf("Base Address configured at %h", m_base_address), UVM_LOW) endfunction endclass ``` Here, during object creation, the driver attempts to fetch its own copy of the base address from the global configuration store. If unsuccessful, fatal error reporting ensures immediate attention towards missing critical information required for proper operation. #### Debugging Path Resolution Issues When encountering issues related to path resolution while working with complex hierarchies involving multiple agents or environments, enabling debug tracing via command line options proves invaluable. By adding `+UVM_CONFIG_DB_TRACE` flag when invoking simulator commands, detailed logs regarding all set/get operations performed throughout runtime become available for analysis[^1]: ```bash irun <other_simulation_options> +UVM_CONFIG_DB_TRACE ``` Such traces help verify whether intended paths correctly resolve down to target objects receiving expected configuration data points. --related questions-- 1. How does one implement custom transaction types compatible with standard UVM components? 2. What are best practices concerning parameterized interfaces used alongside configurable bus slaves? 3. Can you provide examples demonstrating advanced features offered by modern simulators supporting UVM-based projects?
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