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POLinux device model: Same device but different drivers
 

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  1. POLinux device model: Same device but different drivers
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    <p>I'm customising Linux for an ARM9 Atmel AT91SAM960 board. </p> <p>In the <a href="http://lxr.free-electrons.com/source/arch/arm/mach-at91/at91sam9260_devices.c#L901" rel="nofollow">device file</a> Atmel named all the USART the same <code>atmel_usart</code>. Of course with id enumeration:</p> <pre><code>static struct platform_device at91sam9260_uart0_device = { .name = "atmel_usart", .id = 1, .dev = { ...} } </code></pre> <p>According to the Linux Device model, all these devices (5 UARTS on a SAM9260) would be bind to <a href="http://lxr.free-electrons.com/source/drivers/serial/atmel_serial.c#L1638" rel="nofollow">the driver named <code>atmel_usart</code></a>.</p> <p>I don't want to set a TTYS driver on all UARTS which will be registerd. I have several own drivers which serve for different specialised purposes (LON, RS-485 etc.) I want the control which driver does serve a certain USART. So what could I do:</p> <ul> <li><p>The Atmel device files are unsatisfiable and I can do it better. So I rename (patch) the devices in the device file. However, in case I want a TTYS driver on UART4 I would be in trouble. </p></li> <li><p>I manipulate (patch) the device file, so that I'm able the access the structures <code>platform_device</code>. I could change their names before I would register them. But as far as I understood the idea of the <em>Linux Driver Model</em>, devices should be registered early during boot-up but the binding to a driver follows .... later.</p></li> <li><p>I could write a driver, which has an alias name and which would be binded to a specific bus_Id -> <code>atmel_usart.4</code>. Can I really?</p></li> </ul> <p>What solutions else exist. I want to touch a minimal set of Kernel files but <em>I want all the freedom possible?</em></p> <p><strong>Addendum what freedom means to me</strong>: I can specify at runtime how the UARTS can be used</p> <ul> <li>with the Atmel-Serial driver (ttyS)</li> <li>with my own drivers</li> </ul> <p>It means also, that changes to the kernel source are minimal.</p>
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    1. COClarify on what you want to achieve using these changes (all the freedom possible)..Also how many devices would be connected at a time and will the port gets dynamically changed every time you connect the device, like, first time it gets connected to say, uart2 device, next time it would get connected to uart4 device?
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      1. POLinux device model: Same device but different drivers
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    2. COAs it is an embedded device with specific hardware wired to the UARTS, there want be many dynamic changes. The connections are as follow: UART0=Serial Console | UART1=Expansion to other Hardware | UART1=TTYS-Interface to a Bus-System (LON) | UART3=OwnDriver-Interface to a Bus-System (X). But keep in mind how dynamic it can get if Serial-USB devices are used.
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      1. POLinux device model: Same device but different drivers
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