I preface this answer by saying that there were multiple types of chivalric discourse during the Early Modern period. Noel Fallows, building on the work of Pedro Cátedra (particularly his book El sueño caballeresco: De la caballería de papel al sueño real de Don Quijote), notes that these discourses are primarily two: one pertains to "paper chivalry" and the other to "metal chivalry." The former refers to the realm of literature and imaginative art whereas the latter can be understood as the lived experience of the exercise of arms. Here, I will primarily be referring to attitudes towards firearms that we find in chivalric literature, particularly in Italy and in Spain.

One of the clearest literary snapshots of the transition between medieval and early modern warfare comes in the form of Ludovico Ariosto's epic poem Orlando Furioso (~1516). One story arc of the epic (begun in canto 9 and concluded in 11) involves the protagonist Orlando deciding to take up the cause of Olympia, for whom he battles the king Cimosco. The description of this battle calls our attention due to the author's portrayal of the treacherous king:

D'una in un'altra via si leva ratto

di vista al paladin; ma indugia poco,

che torna con nuove armi; che s'ha fatto

portare intanto il cavo ferro e il fuoco:

e dietro un canto postosi di piatto,

l'attende, come il cacciatore al loco

coi cani armati e con lo spiedo, attende

il fier cingial che ruinoso scende...

[Turning from one street then to another, he soon eluded the paladin; but then waited a little before coming back with new weapons; for he had brought meanwhile the iron tube and the fire: and behind a corner he waited for him, like a hunter laying in wait with his armed dogs and spear for the wild boar to come rushing forth...] (emphasis & trad. mine)

Cimosco misses Orlando, and when the paladin approaches him with a frightful countenance - «con sí fiero sembiante aspro ed orrendo, / da far tremar nel ciel Marte si mosse» - the king turns tail and tries to fly from the battle. This battle gives rise to two separate albeit similar invectives against firearms. One of them is delivered in dialogue by Orlando, and the other one by the narrator as an aside to the reader. Orlando calls firearms an «abominoso ordigno» that allow bad knights to boast of prowess which they do not possess. The narrator's railing against firearms is a bit more extreme, for he alleges that guns have effectively brought the nobility of arms to an end:

Come trovasti, o scelerata e brutta

invenzïon, mai loco in uman core?

Per te la militar gloria è distrutta,

per te il mestier de l'arme è senza onore;

per te è il valore e la virtú ridutta

che spesso par del buono il rio migliore...

[How did you ever find, wicked and brute invention, a place in human hearts? Because of you, military glory is destroyed; because of you, the profession of arms is without any honor; because of you, bravery and courage are reduced, since the wicked often seems better than the valiant...]

Across the Mediterranean in Spain, we see similar attitudes towards firearms in chivalric literature. The biggest indicator of a distaste for firearms in chivalric discourse of course comes from Don Quijote's discourse on arms and letters in part 1 of the Quijote; this I will discuss briefly. It is important to note first, however, that the Quijote is itself the byproduct of the popular chivalric literature of the 16th century. Cervantes drew upon the spirit of the Spanish chivalric romances, and many of the Manchegan knight's opinions find their basis or justification in the books that he loved so much.

With that being said, the romances of the 16th century hardly ever included firearms of any kind. This is because chivalric romances were often set in the distant past, such that the most advanced projectile weapon featured would be a spear or a bow. In his article «A Typical Romance of Chivalry», Daniel Eisenberg argues that writers chose to set their books in the remote past so that they would all the more easily pass as histories or chronicles. Be that as it may, this remote past setting calls our attention because it demonstrates that the reading public delighted in reading about deeds of arms, and not those of firearms. Cervantes hints at this in chapter 32 of part 1 of Don Quijote. There, Juan Palomeque talks about the pleasure of reading about the blows described in chivalric romances: «A lo menos, de mí sé decir que cuando oyo decir aquellos furibundos y terribles golpes que los caballeros pegan, que me toma gana de hacer otro tanto, y que querría estar oyéndolos noches y días» [At the very least, I'll say of myself that when I hear described those furious and terrifying blows that the knights strike, I am moved to imitate them, and I could listen to their deeds day in and day out] (trad & emphasis mine).

Finally, in chapter 38 of that same part of the Quijote, don Quijote gives his famous speech on arms and letters. The important thing here is that he, probably influenced by the lack of firearms in his beloved romances, inveighs against guns:

Bien hayan aquellos benditos siglos que carecieron de la espantable furia de aquestos endemoniados instrumentos de la artillería... [los cuales] causa[n] que un infame y cobarde brazo quite la vida a un valeroso caballero, y que sin saber cómo o por dónde, en la mitad del coraje y brío que enciende y anima a los valientes pechos, llega una desmandada bala, disparada de quien quizá huyó y se espantó del resplandor que hizo el fuego al disparar de la maldita máquina...

[May those bygone eras, which lacked the terrifying fury of these damned instruments of artillery, be blessed... the which allow a vile and cowardly man to kill a valorous knight; and, without knowing how or from where, in the middle of a chest filled with the courage that moves brave men, arrives a stray bullet, fired from one who perhaps fled, frightened by the flash issued from the damned machine as it fired...]

Although there are other pieces of literature that can be looked at - such as individual romances of chivalry or perhaps something like Andrés de Claramonte's El valiente negro en Flandes, whose protagonist rises through the ranks of the Spanish military by regressing to fighting with close-quarter weapons - I think the above ought to suffice to get an idea of how firearms were seen in chivalric literature. Of course, the opinions of writers don't necessarily have to reflect those of soldiers on the battlefield nor those of monarchs or other rulers.

Bibliography:

Ariosto, Ludovico. Orlando Furioso, ed. Natalino Sapegno. Principato Editore, 1972.

Cervantes, Miguel de. El ingenioso caballero don Quijote de la Mancha. < http://www.cervantesvirtual.com/obra-visor/el-ingenioso-hidalgo-don-quijote-de-la-mancha--0/html/fef04e52-82b1-11df-acc7-002185ce6064_2.html#I_0_ >

Eisenberg, Daniel. «A Typical Romance of Chivalry». < http://www.cervantesvirtual.com/obra-visor/romances-of-chivalry-in-the-spanish-golden-age-0/html/ffcd58ce-82b1-11df-acc7-002185ce6064_37.html#I_7_ >

Fallows, Noel. Jousting in Medieval and Renaissance Iberia. Boydell Press, 2010.