September 2011
Intermediate to advanced
744 pages
19h 4m
English
Content preview from Professional Windows® Embedded Compact 7
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DRIVER CONTEXT
A Stream Driver has two types of contexts. One is for the driver, and the other is for any streams opened with it.
Device Context
As mentioned previously, the driver context is established in XXX_Init, and there is only one driver context for each loaded driver. This context is represented by a structure that stores information about the driver that it gets from its registry entries. The structure is specific to the driver. The number of instances of the driver are stored in the device context, so XXX_Init can limit the number of such instances. The number of opened streams to the driver can also be a device context and can be used to limit the number of such streams that are open. If multiple streams are permitted, the device driver needs to employ multitasking mechanisms to function currently. A typical code for XXX_Init is shown here.
PDEVCONTEXT pDevContext; HKEY hKey; //Get registry information hKey = RegDeviceOpen((LPCWSTR)pContext); . . . . . . . . RegCloseKey(hKey); //Check whether driver has been loaded, and check its index . . . . . . . . //Create an instance of the device context on the heap pDevContext = (PDEVCONTEXT)LocalAlloc(LPTR,sizeof(DEVCONTEXT)); if (pDevContext == NULL){ return NULL; } // Initialize the device context pDevContext->hMsgQ=NULL; pDevContext->dwSize = sizeof(DEVCONTEXT); . . . . . . . . pDevContext->OpenCount = 0; InitializeCriticalSection(&pDevContext->CS); ...Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.