Linux Device Driver >> Assembly (ARM)

workqueue


參考資訊:
1. ldd

在延遲中斷處理機制上,workqueue是另一個可以使用的方式,workqueue是執行在低優先級別上,因此,可以讓Context Switch繼續執行,意味著使用者可以在workqueue裡面呼叫sleep()相關的函式,這也是跟softirq、tasklet最大的差別,因此,workqueue是相當適合應用在耗時處理的場合

使用步驟:
1. __alloc_workqueue_key()
2. queue_work_on()
3. destroy_workqueue()

ldd.S

    .global init_module
    .global cleanup_module

    .equ BUTTON, 27
    .equ IRQF_TRIGGER_RISING, 1

    .section .modinfo, "ae"
__UNIQUE_ID_0: .asciz "license=GPL"
__UNIQUE_ID_1: .asciz "author=Steward Fu"
__UNIQUE_ID_2: .asciz "description=Linux Driver"

    .equ work_struct.data,       0
    .equ work_struct.entry,      4
    .equ work_struct.entry.next, 4
    .equ work_struct.entry.prev, 8
    .equ work_struct.func,       12

    .struct 0
work_struct_s:
    i0: .struct . + 4
    i1: .struct . + 8
    i2: .struct . + 4
work_struct_e:
work_struct_l = work_struct_e - work_struct_s

    .section .data
btn_irq:     .dcb 4
irq_name:    .asciz "gpio_irq"
work_name:   .asciz "myworkqueue"
work_msg:    .asciz "workqueue_handler\n"
mywork:      .space work_struct_l
myworkqueue: .dcb 4

    .align 2
    .section .text
workqueue_handler:
    push {lr}
    ldr r0, =work_msg
    bl printk
    pop {pc}

irq_handler:
    push {lr}
    mov r0, #2
    ldr r1, =myworkqueue
    ldr r1, [r1]
    ldr r2, =mywork
    bl queue_work_on
    mov r0, #1
    pop {pc}

init_module:
    push {r4, r5, lr}

    ldr r0, =work_name
    mov r1, #0
    mov r2, #0
    mov r3, #0
    mov r4, #0
    push {r4}
    bl __alloc_workqueue_key
    pop {r4}
    ldr r1, =myworkqueue
    str r0, [r1]

    ldr r0, =mywork
    add r0, #work_struct.data
    ldr r1, =#0xffffffe0
    str r1, [r0]

    ldr r0, =mywork
    add r0, #work_struct.entry @next
    mov r1, r0
    str r1, [r0]
    add r0, #work_struct.entry @prev
    str r1, [r0]

    ldr r0, =mywork
    add r0, #work_struct.func
    ldr r1, =workqueue_handler
    str r1, [r0]

    mov r0, #BUTTON
    bl gpio_to_desc
    bl gpiod_to_irq
    ldr r1, =btn_irq
    str r0, [r1]

    ldr r1, =irq_handler
    mov r2, #0
    mov r3, #IRQF_TRIGGER_RISING
    ldr r4, =irq_name
    mov r5, #0
    push {r4, r5}
    bl request_threaded_irq
    pop {r4, r5}

    mov r0, #0
    pop {r4, r5, pc}

cleanup_module:
    push {lr}
    ldr r0, =btn_irq
    ldr r0, [r0]
    mov r1, #0
    bl free_irq
    ldr r0, =myworkqueue
    ldr r0, [r0]
    bl destroy_workqueue
    pop {pc}
    .end

init_module: 設定GPIO中斷以及workqueue延遲處理副程式
irq_handler: 安排一個workqueue延遲處理
workqueue_handler: 列印字串
cleanup_module: 釋放中斷資源以及刪除workqueue

完成

# workqueue_handler


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