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84 lines
2.5 KiB
C++
84 lines
2.5 KiB
C++
#pragma once
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// Device is the base class of everything that lives in the /dev directory.
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//
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// All Devices will automatically register with the VFS.
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// To expose a Device to the filesystem, simply pass two unique numbers to the constructor,
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// and then mknod a file in /dev with those numbers.
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//
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// There are two main subclasses:
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// - BlockDevice (random access)
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// - CharacterDevice (sequential)
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//
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// The most important functions in Device are:
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//
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// class_name()
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// - Used in the /proc filesystem to identify the type of Device.
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//
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// read() and write()
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// - Implement reading and writing.
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// - Return the number of bytes read/written, OR a negative error code.
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//
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// can_read() and can_write()
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//
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// - Used to implement blocking I/O, and the select() and poll() syscalls.
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// - Return true if read() or write() would succeed, respectively.
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// - Note that can_read() should return true in EOF conditions,
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// and a subsequent call to read() should return 0.
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//
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// ioctl()
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//
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// - Optional. If unimplemented, ioctl() on the device will fail with -ENOTTY.
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// - Can be overridden in subclasses to implement arbitrary functionality.
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// - Subclasses should take care to validate incoming addresses before dereferencing.
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//
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#include <AK/Retainable.h>
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#include <AK/Types.h>
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#include <Kernel/FileSystem/FileDescriptor.h>
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class Process;
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class Device : public Retainable<Device> {
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public:
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virtual ~Device();
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InodeMetadata metadata() const { return { }; }
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virtual KResultOr<Retained<FileDescriptor>> open(int options);
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virtual void close();
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virtual bool can_read(Process&) const = 0;
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virtual bool can_write(Process&) const = 0;
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virtual ssize_t read(Process&, byte*, ssize_t) = 0;
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virtual ssize_t write(Process&, const byte*, ssize_t) = 0;
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unsigned major() const { return m_major; }
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unsigned minor() const { return m_minor; }
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virtual bool is_tty() const { return false; }
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virtual bool is_master_pty() const { return false; }
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virtual int ioctl(Process&, unsigned request, unsigned arg);
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virtual const char* class_name() const = 0;
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uid_t uid() const { return m_uid; }
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uid_t gid() const { return m_gid; }
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virtual bool is_block_device() const { return false; }
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virtual bool is_character_device() const { return false; }
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protected:
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Device(unsigned major, unsigned minor);
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void set_uid(uid_t uid) { m_uid = uid; }
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void set_gid(gid_t gid) { m_gid = gid; }
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private:
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unsigned m_major { 0 };
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unsigned m_minor { 0 };
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uid_t m_uid { 0 };
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gid_t m_gid { 0 };
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};
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