{"id":7984,"date":"2022-03-01T08:15:08","date_gmt":"2022-03-01T08:15:08","guid":{"rendered":"http:\/\/fastbitlab.com\/?p=7984"},"modified":"2023-09-14T16:32:15","modified_gmt":"2023-09-14T11:02:15","slug":"linux-device-driver-programming-lecture-39-understanding-read-method","status":"publish","type":"post","link":"https:\/\/fastbitlab.com\/blog\/linux-device-driver-programming-lecture-39-understanding-read-method\/","title":{"rendered":"Linux Device Driver Programming Lecture 39- Understanding read method"},"content":{"rendered":"
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Understanding read method<\/b><\/span><\/h1>\n
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In this article, let’s understand our driver’s read method implementation.<\/span><\/p>\n

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Figure 1. Read method implementation<\/span><\/figcaption><\/figure>\n

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What is read? <\/strong><\/span><\/p>\n

The user-level process executes a read system call to read from a file. In our case, the file is not a regular file but a device file, which handles our pseudo character device.<\/span><\/p>\n

In our project, the pseudo character device is nothing but a memory array. A contiguous memory location an array. So, I will call it as a device memory buffer. Whenever a user program issues read system call on our device file, we should transfer data from our device memory buffer to the user buffer. So, the data copy happens from kernel side to user side. That is read. <\/span><\/p>\n

The write is in reverse direction, write means user program wants to write some data into the device memory buffer of our device.<\/span><\/p>\n

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Purpose of the Read Method:<\/strong><\/span><\/p>\n