LUN address is essentially how people used to address SCSI devices back
in the day we had these devices more in use. However, SCSI was taken as
an abstraction layer for many Unix and Unix-like systems, so it still
common to see LUN addresses in use. In Serenity, we don't really provide
such abstraction layer, and therefore until now, we didn't use LUNs too.
However (again), this changes, as we want to let users to address their
devices under SysFS easily. LUNs make sense in that regard, because they
can be easily adapted to different interfaces besides SCSI.
For example, for legacy ATA hard drive being connected to the first IDE
controller which was enumerated on the PCI bus, and then to the primary
channel as slave device, the LUN address would be 0:0:1.
To make this happen, we add unique ID number to each StorageController,
which increments by 1 for each new instance of StorageController. Then,
we adapt the ATA and NVMe devices to use these numbers and generate LUN
in the construction time.
Each of these strings would previously rely on StringView's char const*
constructor overload, which would call __builtin_strlen on the string.
Since we now have operator ""sv, we can replace these with much simpler
versions. This opens the door to being able to remove
StringView(char const*).
No functional changes.
Function-local `static constexpr` variables can be `constexpr`. This
can reduce memory consumption, binary size, and offer additional
compiler optimizations.
These changes result in a stripped x86_64 kernel binary size reduction
of 592 bytes.
Add polling support to NVMe so that it does not use interrupt to
complete a IO but instead actively polls for completion. This probably
is not very efficient in terms of CPU usage but it does not use
interrupts to complete a IO which is beneficial at the moment as there
is no MSI(X) support and it can reduce the latency of an IO in a very
fast NVMe device.
The NVMeQueue class has been made the base class for NVMeInterruptQueue
and NVMePollQueue. The factory function `NVMeQueue::try_create` will
return the appropriate queue to the controller based on the polling
boot parameter.
The polling mode can be enabled by adding an extra boot parameter:
`nvme_poll`.
Apologies for the enormous commit, but I don't see a way to split this
up nicely. In the vast majority of cases it's a simple change. A few
extra places can use TRY instead of manual error checking though. :^)
Only a generic struct definition was present for NVMeSubmission. To
improve type safety and clarity, added an union of NVMeSubmission
structs that are applicable to the command being submitted.
The CAP.TO is 0 based. Even though I don't see that mentioned in the
spec explicitly, all major OSs such as Linux, FreeBSD add 1 to the
CAP.TO while calculating the timeout.
IO::delay was added as a lazy alternative to looping with a timeout
error if the condition was not satisfied. Now that we have the
wait_for_ready function, remove the delay in the reset and start
controller function.
This mostly just moved the problem, as a lot of the callers are not
capable of propagating the errors themselves, but it's a step in the
right direction.
We need to use the volatile keyword when mapping the device registers,
or the compiler may optimize access, which lead to this QEMU error:
pci_nvme_ub_mmiord_toosmall in nvme_mmio_read: MMIO read smaller than
32-bits, offset=0x0
Add a basic NVMe driver support to serenity
based on NVMe spec 1.4.
The driver can support multiple NVMe drives (subsystems).
But in a NVMe drive, the driver can support one controller
with multiple namespaces.
Each core will get a separate NVMe Queue.
As the system lacks MSI support, PIN based interrupts are
used for IO.
Tested the NVMe support by replacing IDE driver
with the NVMe driver :^)
