writing linux device drivers a guide with exercises pdf download

Ngày tải lên: 09/08/2014, 04:21

Ngày tải lên: 13/08/2014, 21:21

Ngày tải lên: 13/08/2014, 21:21

Ngày tải lên: 13/08/2014, 21:21

Ngày tải lên: 13/08/2014, 21:21

Ngày tải lên: 13/08/2014, 21:21

... mount a filesystem. Network interfaces Any network transaction is made through an interface, that is, a device that is able to exchange data with other hosts. Usually, an interface is a hardware ... user programs are an integral part of a software package and that even policy-free packages are distributed with configuration files that apply a default behavior to the underlying mechanisms. ... the large and growing Linux user base to their potential markets. And the open source nature of the Character devices A character (char) device is one that can be accessed as a stream of...

Ngày tải lên: 24/12/2013, 01:17

... software system (such as the kernel) must be aware of and avoid namespace pollution. Namespace pollution is what happens when there are many functions and global variables whose names aren't ... can check what ports are already in use and set up the new device to use an available I/O range. Although you might object that most modern hardware doesn't use jumpers any more, the ... might seem hairy, we must keep in mind that Linux is an SMP- compliant system, and a global variable simply won't work when you are file had the same format, but without the "layered"...

Ngày tải lên: 24/12/2013, 01:17

... and a practical one. Philosophically, it's always a bad idea to put arbitrary limits on data items being managed. Practically, scull can be used to temporarily eat up your system's ... through an array of intermediate pointers. The released source uses an array of 1000 pointers to areas of 4000 bytes. We call each memory area a quantum and the array (or its length) a quantum ... whereas virtual consoles and serial terminals are managed by driver 4; similarly, both vcs1 and vcsa1 devices are managed by driver 7. The kernel uses the major number at open time to dispatch...

Ngày tải lên: 24/12/2013, 01:17

... is a fairly typical read_procimplementation. It assumes that there will never be a need to generate more than one page of data, and so ignores the start and offset values. It is, however, careful ... memory waste by overwriting old data should nobody read it. Another feature of the Linux approach to messaging is that printk can be invoked from anywhere, even from an interrupt handler, with ... that the /proc file looks like a FIFO, in that the reader blocks, waiting for more data. Obviously, you can't read messages this way if klogd or another process is already reading the same...

Ngày tải lên: 24/12/2013, 01:17

... value, and some take a pointer to other data. Using a pointer is the way to pass arbitrary data to the ioctl call; the device will then be able to exchange any amount of data with user space. ... because data is already available when read is issued. Similarly, no output buffer was used, because data is simply copied to the memory area associated with the device. Essentially, the device ... represent not a variable number of arguments. In a real system, however, a system call can't actually have a variable number of arguments. System calls must have a well-defined number of arguments...

Ngày tải lên: 24/12/2013, 01:17

... provided by a device driver to handle asynchronous tasks which, usually, are too large to be done while handling a hardware interrupt. This chapter should make sense without an understanding of ... timers are organized in a doubly linked list. This means that you can create as many timers as you want. A timer is characterized by its timeout value (in jiffies) and the function to be called ... long data; /* argument to the handler */ can't atomically access both the timeval fields tv_sec and tv_usec unless you disable interrupts. As of the 2.2 kernel, a quick and safe way of...

Ngày tải lên: 24/12/2013, 01:17

... SLAB_NO_REAP SLAB_HWCACHE_ALIGN SLAB_CACHE_DMA Flags that can be specified while creating a cache. SLAB_CTOR_ATOMIC You can find the exact values used for the allocation blocks in mm/kmalloc.c ... doesn't actually allocate any memory. The return value of ioremap is a special virtual address that can be used to access the specified physical address range; the virtual address obtained ... memory area that is several (physically contiguous) pages long, but doesn't zero the area. __get_dma_pages Similar to get_free_pages, but guarantees that the allocated memory is DMA capable....

Ngày tải lên: 24/12/2013, 01:17

... it's not always possible when dealing with older hardware. Backward Compatibility Happily, little has changed with regard to basic hardware access. There are just a few things that need ... = phys_addr & ~PAGE_MASK; /* Adjust the begin and end to remap a full page */ phys_addr &= PAGE_MASK; size = PAGE_ALIGN(last_addr) - phys_addr; return ioremap(phys_addr, size) ... instantiation is platform dependent. An rmb (read memory barrier) guarantees that any reads appearing before the barrier are completed prior to the execution of any subsequent read. wmb guarantees...

Ngày tải lên: 24/12/2013, 01:17

... what it can do. These restrictions are the same as those we saw with task queues. A handler can't transfer data to or from user space, because it doesn't execute in the context of a ... process. Handlers also cannot do anything that would sleep, such as calling sleep_on, allocating memory with anything other than GFP_ATOMIC, or locking a semaphore. Finally, handlers cannot call ... simply a signal that the hardware can send when it wants the processor's attention. Linux handles interrupts in much the same way that it handles signals in user space. For the most part, a...

Ngày tải lên: 24/12/2013, 01:17

... items in addition to standardizing on a specific endianness. Natural alignment means storing data items at an address that is a multiple of their size (for instance, 8-byte items go in an address ... to access unaligned data for example, how to read a four-byte value stored at an address that isn't a multiple of four bytes. PC users often access unaligned data items, but few architectures ... Most modern architectures generate an exception every time the program tries unaligned data transfers; data transfer is handled by the exception handler, with a great performance penalty. If...

Ngày tải lên: 24/12/2013, 01:17

... memory), and having that many drivers trying to probe for hardware would be a near-certain way to create conflicts and confusion. With automatic loading, the kernel can adapt itself to the hardware ... before any path directives, you can cause modprobe to add new paths to the list instead of replacing it. alias alias_name real_name Causes modprobe to load the module real_name when asked to load ... system. [42]The ALSA drivers can be found at www.alsa-project.org. Another common use of automatic module loading is to make a "one size fits all'' kernel to package with distributions....

Ngày tải lên: 21/01/2014, 07:20

... arrays are used. There is one read_ahead[] value for each major number, and it applies to all its minor numbers. max_readahead, instead, has a value for every device. The values can be changed ... default. hardsect=512 (bytes) The sbull sector size is the usual half-kilobyte value. rahead=2 (sectors) Because the RAM disk is a fast device, the default read-ahead value is small. In Linux ... major and minor numbers. Reading data before a process asks for it helps system performance and overall throughput. A slower device should specify a bigger read- ahead value, while fast devices...

Ngày tải lên: 21/01/2014, 07:20

... parameter that controls memory allocation. The reason for this is that vmalloc allocates its pages one at a time, because single-page allocations are far more likely to succeed than multipage ... programs running on the system can allocate far more memory than is physically available; indeed, even a single process can have a virtual address space larger than the system's physical ... Mapping a device means associating a range of user-space addresses to device memory. Whenever the program reads or writes in the assigned address range, it is actually accessing the device. ...

Ngày tải lên: 21/01/2014, 07:20

... Some flags are managed by the kernel, and some are set by the interface at initialization time to assert various capabilities and other features of the interface. The valid flags, which are defined ... modified and the packet has been received. For example, a packet aimed at 192.168.0.32 will leave through sn0 and reappear at sn1 with a destination address of 192.168.1.32, which is not a local address ... largest possible packet, the driver should stop the queue until space becomes available again. Transmission Timeouts Most drivers that deal with real hardware have to be prepared for that...

Ngày tải lên: 21/01/2014, 07:20