TP-Link TL-WR741ND v1.9 upgrade to 18.06.x possible?

EDIT: TL;DR answer is YES, it's possible (see slh's answer below)

Hello all,

my question is regarding hardware version 1.9 of the TL-WR741ND router.

Is it possible to upgrade to 18.06 from 17.01 on this particular variant?

I ask this, because on the device's ToH page, this particular hw version (along with v1.4, v1.5 and v3) does not have a corresponding "Current Release" - it's blank.
A few lines below, there is this in the Model Specific Notes "v1.9 has a different flash chip compared to other v1.x models" and the techdata page (https://openwrt.org/toh/hwdata/tp-link/tp-link_tl-wr741nd_2) shows it to be "ar71xx" instead of "ar71xx-ath79" for the v1 [apologies, but can still only post two links, so for this one, just put a "1" instead of "2" at the end].

I am currently running 17.01.4 and do not remember there being some restriction on this hw version back when I did the install at the end of 2017, so do I ignore and install the tiny version for the v1 or consider the v1.9 unsupported for 18.06. If the latter is the case, can I as an average Joe update the wiki to make it clear for others with the same hw? Thanks

Usually for TP-Link hardware all subrevisions (x.9) of a major hardware revision (1.x) are covered in a single firmware image, this means the difference between them are so minor (this can be production changes like replacing one NOR flash with another type or merely software differences --> newer firmware version preinstalled) that they can be supported by a single firmware image (not necessarily backwards compatible --> requiring a minimum version to cover all known variants) of the OEM firmware; so far I don't know of any exceptions to this rule of thumb for OpenWrt either. This means a single firmware image should cover all (known) hardware variants of the TL-WR741ND v1.x, including your v1.9. The device page for your device and the bugtracker- and git history for it seems support this information.

The ar71xx target covering the QCA-Atheros SOCs in question is mach-file based, an old method of telling the kernel of the hardware specifics for the device in question. A newer replacement for these mach-files would be describing this very low level hardware information using the device tree infrastructure, ath79 is the target name for this covering the very same QCA-Atheros SOCs. Both are different ways to support and set up the same hardware, but the linux mainline kernel only accepts the later for newly submitted devices (which aren't self-describing (e.g. via BIOS/UEFI + ACPI + SMM)/ can't be auto-probed), this is why efforts are underway to replace ar71xx with ath79 and to port (hopefully all) ar71xx mach-files to device tree and ath79, allowing them to be submitted to future linux mainline kernel versions. OpenWrt versions prior to- and including 18.06.x only support the mach-file based ar71xx target, while current master (snapshots) and the upcoming 19.03.x will start to support a subset of devices (already including yours) with both ar71xx or ath79; future OpenWrt versions will drop ar71xx in favour or ath79 alltogether (hopefully not leaving any, or at least not many, devices behind).

The (new in 18.06.x and later) tiny subtarget is an approach to trim down the firmware size, allowing it to (maybe) fit into 4 MB flash devices again. For all intents and purposes it is equivalent to the former non-tiny variants, you can cross-grade in both directly

Yes, your device is supported by 18.06.2, but given that it is a low-end device with 4 MB flash and 32 MB RAM, https://openwrt.org/supported_devices/432_warning applies - which is becoming a serious issue going forward (there've been plenty of topics regarding this recently, look through the forum for details). 18.06.x is probably the last OpenWrt release which can support these devices at all and it already is hard on the limit of feasibility. Looking forward you will have to replace your hardware with something more capable, for a while you may be able to keep your device on life support by trimming down firmware size and number of running services using imagebuilder or building from source, but the situation is tight at best. Also keep in mind that only 17.01.x and 18.06.x currently have any kind of security support, with 17.01.x's EOL date being imminent; with 19.03.x being released soon.

Running current and maintained versions of OpenWrt is crucial for security reasons, this may involve replacing devices that can no longer support these; devices falling into the 4/32 category are at the brink (and beyond) of being supportable.

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Wow. When it comes to getting questions answered, it doesn't come better than this. slh, thank you so much!

Just ran the sysupgrade and if anyone else should come across this, I can confirm that it worked without issues.

Re keeping up with current builds, I fully agree and admit this was my bad. I should know better. That said, this isn't a public facing router (just a secondary AP at home) and so wifi being the biggest weakness, the KRACK vulnerability was the last big one I heard of and that was fixed in 17.01.4.
Until I get something like the Turris Omnia with their auto-updates, I should probably schedule a quarterly reminder or something. I'm not that tech-savvy - so things like building my own images to keep under the 4MB limit is currently beyond my skillset (but appreciate the suggestion) - so I am sure there is some better way in keeping up-to-date with these sort of things (mailing list, RSS of the release notes page? dunno).

Last question, am I allowed to clean up the ToH wiki entry or is that locked down for general users? I accept that these 4MB devices probably won't make it into 19.03 and so the wiki won't be relevant for much longer, but it's the least I could do.

The wiki depends on volunteers keeping it up to date, particularly for device specific information. Usually just about anything can be changed by registered users (there is no shared single-sign-on between forum and wiki, so you'd need register there as well), so you're certainly welcome and encouraged to do so.

While releases are announced to forum and mailing list, there is no dedicated mailing list for release announcements - meaning it will be difficult (not really possible) to filter it down to 'just' release notes. A substitute may be subscribing to github's release feed, but keep in mind that github is only a mirror of git.openwrt.org - and that you'll only see when a release gets tagged, not when it has actually been pushed to the mirror (building OpenWrt in its entirety for a release takes up to two days, partial binaries will show up on the mirror before that).

While the Turris Omnia is an amazing piece of hardware, it's also very much on the high financial end - beyond the prices for comparable hardware (small production runs are always more expensive than mass-produced hardware). You can already find rather amazing hardware for 5-20 EUR on the used market, sometimes even including concurrent dual-band support and 802.11ac (lantiq+ath9k/ath10k). New single-band devices start a tad below 20 EUR (ar71xx/ ath79), with the first useful concurrent dual-band 802.11ac devices (mt7621) starting around 35 EUR new. Depending on your WAN connection speed, very capable devices can be bought new for around 65 EUR (ipq40xx). All of the devices suggested here have no problems to support OpenWrt for the forseeable future (with 16/128 MB at least, several significantly beyond that). Supported devices don't need to be expensive.

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